For months, Russia has been making advances into eastern Ukraine.

And today, Russian forces are claiming to have captured Serhiivka, about 15km (9 miles) from Pokrovsk.

Pokrovsk - located about 70km (43 miles) north-west of Russian-held Donetsk city - is a key logistics hub for Ukraine.

It sits on the intersection of a main road that supplies Ukrainian troops and towns across the eastern front.

In recent weeks, Russia has inched closer to the outskirts of Pokrovsk, taking a string of tiny villages towards the city, with Moscow claiming Lysychne and Ivanivka, both north of Serhiivka and close to Pokrovsk.

Yesterday, the head of the city's military administration Sergiy Dobryak urged residents of Pokrovsk, especially families, to evacuate as Russia was "rapidly approaching the outskirts".

Image source, Reuters

Russia's border defences "were not prepared" for Ukraine's multi-battalion assault, according to the British Ministry of Defence.

Russia's initial response was "disarray and disorganisation," the ministry says in an update on social media.

But Russian forces have now been redeployed from elsewhere along the border and they are building "additional defensive positions in an effort to prevent Ukrainian advances".

The intelligence update also confirmed that Ukrainian troops have penetrated the Kursk region "to a depth ranging between 10-25km over a frontage of approximately 40km" since the incursion began.

Thomas Copeland
Live reporter

Getting Russia to negotiate on Ukraine's terms is one of the objectives behind its incursion into Russia, a senior aide to President Zelensky says.

"Ukraine is not interested in occupying Russian territories," explains Mykhailo Podolyak in a statement on social media.

"But if we are talking about potential negotiations – I emphasize potential – we will have to put [Russia] at the table opposite. On our own terms."

Ukraine showing that it is capable of occupying Russian territory would be a "proven, effective means of coercion" to force Russia into negotiations, Podolyak says.

"In the Kursk region, we can clearly see how the military tool is being used objectively to persuade [Russia] to enter a fair negotiation process," he says.

Podolyak says that the incursion will also influence public opinion because "the Russians were obviously scared. They are shocked," by the ability of Ukraine's forces to enter Russian territory.

"Negative changes in the psychological state of the Russian population will be another argument for the start of negotiations," he says.

Savill is asked for his final thoughts about where the conflict is going, a question asked by a lot of listeners.

He says he initially thought the current situation was intended to create tactical pressure on Russian forces in northern Ukraine, making a powerful point about morale and Ukrainian strength.

In the last 48 hours he says Ukraine has talked about whether it intends to consolidate a bit more, which Savill says would be incredibly risky if it tries to stick it out through to negotiations.

He says he suspects there will be more of a consolidation and a withdrawal to more defensible lines, but finishes by saying "who knows?".

The sixth - and final - question comes from Dennis in Berkshire: Good day Ukrainecast. Whilst walking my Rhodesian Ridgeback and listening to your last podcast, I too pondered how Putin will respond to the invasion by Ukrainian forces into Kursk. My question is, could Putin deploy tactical nuclear weapons to drive out the Ukrainian ground troops? I’d be interested in your views.

Savill says this is where we enter the field of broad speculation.

The Russians have consistently made threats about nuclear weapons. The Ukrainians would argue with some force that they have called Russia's bluff several times.

The Russians would not hesitate to use serious firepower inside Russia on their own urban areas to eject the Ukrainians. But it's hard to see the Russians using a tactical nuclear weapon on their own territory, says Savill.

They might threaten it against Ukraine, but in truth their retaliation against Ukraine is more likely to be a ramping up of their long-range strike campaign against Ukrainian infrastructure, power generators and other civilian targets to inflict political pain on Zelensky, particularly as winter approaches.

Shevchenko says the Russians keep mentioning nuclear weapons all the time. But, he asks Savill, perhaps the more you make this threat, the less effective it becomes?

It's almost parody at the moment, says Savill. We shouldn't be blasé about the risks of escalation with a nuclear-armed power but it's mostly in Russian interests to keep this conflict conventional, because they have a lot of conventional advantages.

Image source, Getty Images

The fifth question comes to us from Joanna in West Yorkshire: Hi Ukrainecast, the Kursk invasion has brought the war in Ukraine back onto the news agenda. How else might this affect attitudes in the West? Might it for example encourage more generous donations? Your thoughts - thank you!

Savill says the Ukrainian brigades appear to have been equipped with some of the Western-supplied artillery and vehicles.

He suggests the incursion could be intended to demonstrate to the West that there should be more support internationally – the Ukrainians have already said they would like restrictions eased on long-ranged weapons.

It doesn't seem as if the Ukrainians told their Western allies about the incursion ahead of time, which is different to the broader counter offensive last year, he says.

The slow ratcheting up of international support was for a long time very successful, as small incremental steps that are never seen to justify a large reaction. There is an argument now about whether that strategy has been too slow to adapt.

On the question of whether the incursion could change minds in Washington, particularly among those who have been sceptical of providing more support for Ukraine, Savill says it could.

He says it feels like the intent is to send a message to the US system: we are winners, back us.

With that, our live stream of Ukrainecast - where they've been answering listeners' questions - is over.

However, there was quite a lot to get through in that half-hour so we'll bring you some more of what was discussed here on this page in the coming minutes.

For more episodes of Ukrainecast, head to their homepage here.

The fourth question is asked by Hugh in Cheshire who is calling in live: How have Ukrainian soldiers been behaving during the incursion into Russia over the past week? We heard a lot about the barbarity and savagery and wanton destruction that took place when Russia invaded in Feb 2022 - Bucha being a prime example. Now that the boot is on the other foot, is that savagery and destruction being reciprocated?

Savill says there's a strong incentive for Ukrainians to contrast appropriate behaviour with that of the Russians.

He says there isn't consistent and extensive reporting of what's going on inside Russia at the moment and that's because Ukraine is keen to maintain security.

There is talk of a humanitarian corridor being opened up and Savill says Ukraine is acting in line with its obligations, from what we've seen so far.

Although he says it is almost inevitable there will be injuries and deaths in an area with a lot of civilians.

Shevchenko goes on to say there is no hard evidence that Ukrainian troops have been misbehaving in Kursk.

In March 2022, invading Russian troops occupied the Ukrainian town of Bucha outside Kyiv, leaving a trail of death and destruction which shocked the world.

Another question on Discord - this from Josh: ‘How long can Ukraine feasibly hold this territory? And how much is there a discussion within Ukraine of the trade-off between defending its territory and this invasion?’

Savill of the Royal United Services Institute think tank says how long Ukraine will be able to hold on to this territory depends on the amount of resources they devote to the offensive and how they "might weaken themselves" elsewhere.

He says there is evidence that Ukrainians had to move highly experienced combat troops from other key frontlines to carry out this incursion.

This means that "mechanised forces" who can "strike hard" could carry out the attacks, he says, but Ukraine "wouldn't want to be holding this for months" as it will make them "more vulnerable" to Russian artillery attacks and air strikes.

Savill points out that this potential danger is possibly why Kyiv is hitting airbases within Russia.

Shevchenko also says that the word in Kyiv is "nobody is saying they want to stay" and the objective is to stop Russian attacks and missiles hitting the Ukrainian border region of Sumy.

The trio also discuss the potential for Ukraine to exchange territory it has captured to regain areas taken by Russia - an idea which is "unofficially" touted in Kyiv.

Image source, Getty Images

Here is another question - this time from Sasha, who asked Ukrainecast how likely is it that Russian forces can cut off the Ukrainian troops currently occupying Russian territory?

At the moment, there is probably no chance of this because the Ukrainians are still expanding outwards, Rusi's Savill says.

But they will have a challenge depending on how long they choose to stay and defend those supply lines from Russian airstrikes and attacks.

If they choose to extend further, they might outrun their own logistics supply lines.

And if they try and hold on to particular settlements in the face of an eventual Russian counter-attack, that will be a challenge too, he says.

There are a few signs that they might be digging in, but so far they haven't set up the kind of deep defences needed to repel a Russian counter-attack, Savill adds.

Image source, Getty Images

The first question on Ukrainecast is from Duncan in Western Australia. He asks: Can you describe the topography where Ukrainian incursion into Russia occurred? Is it like flat country, rolling country, is that a river or highway that separates the border? And what do you know about what level of defences the Russians had?

Presenter Vitaly Shevchenko says there is a lot of flat land, with small wooded areas, no major rivers or big roads that would act as obstacles.

There are a couple of relatively good roads though, and all that made it easier for the Ukrainian forces to move into the Kursk region, he explained.

Defence expert Matthew Savill, from the Royal United Services Institute, then moved on to the second part of the question, saying it seems the area had been not well defended.

Russia had a combination of internal security and border forces there and not much in the way of large conventional forces, he says.

The area hasn't had the kind of deep defensive lines the Ukrainians have found difficult to break through in Ukraine itself, he says, adding that they seem to have deliberately chosen a weak spot on the border.

Image source, .

The Ukrainian incursion into Russia last week has surprised many and adds an extra layer of complexity to an already complicated picture.

A special episode of Ukrainecast today aims to shed some light on events for those with outstanding questions.

Presenters Lucy Hockings and Vitaly Shevchenko will be joined by defence expert Matthew Savill from the Royal United Services Institute, a leading UK defence think tank, a little later today to answer listeners' questions.

We will bring you the latest lines from the episode, which you can follow along by pressing the Watch live button at the top of this page from 12:30 BST.

Jonathan Beale
Defence correspondent

Image source, EPA

Ukraine’s advance into Russia has slowed in recent days and there’s likely to be a point soon when it stops.

There’ll be more logistical challenges the further Ukraine advances – keeping forces supplied with ammunition, food and fuel.

But that’s not a significant obstacle given that Ukraine’s troops are still within 50km of their own border.

The greater concern will be holding on to the gains made – long enough for it to be a bigger political problem for President Putin and a drain on Russia’s own forces.

There’s already evidence that Ukraine has been digging in and building defences. But those defences will become a magnet for Russian attacks.

Moscow has already been releasing video of its air force using glide bombs to target Ukrainian positions on its side of the border. The same weapons which have had such a devastating effect in eastern Ukraine.

Justin Crump, a former British Army Officer and who now heads the risk consultancy Sibylline, says over time Ukrainian forces across the border will become more vulnerable to Russian attacks. He says the chances of Russia attacking Ukraine’s supply lines and using its Air Force effectively will increase.

The morale boost for Ukraine in launching this offensive could soon dissipate if this becomes another grinding, static battle.

Ukraine releases footage of first day of incursionpublished at 12:08 British Summer Time 16 August

12:08 BST 16 August

By Richard Irvine-Brown

Ukraine’s armed forces have published footage on social media of their assault on a Russian border checkpoint near Sudzha, in the Kursk region, on 6 August, the first day of their incursion into Russia.

The video shows buildings at the checkpoint being fired on, and some destroyed. The video ends with a Ukraine-marked tank driving north, toward Sudzha.

We verified the location by matching the layout of roads and buildings at the checkpoint to satellite images available on Google, Bing and others.

We can even tell where the tank is driving by the road markings and the number of lanes on a road near the checkpoint.

We know this was filmed on 6 August because proprietary satellite images show all the buildings intact on 5 August, and damaged on 6 August.

Given the shadows, the attack must have been filmed in the early evening, between about 17.30 and 19:00, local time.

The light wind and scattered cloud cover also matches weather reports for Sudzha at this time.

Russia's air defence systems repelled a strike on the Crimean bridge last night by 12 US-made missiles, the defence ministry says in a statement on Telegram.

The missiles are said to have been targeting the landmark bridge built on president Putin's orders after Russia annexed the Crimean peninsula in 2014.

The strike consisted of "12 ATACMS operational-tactical missiles made in the US", according to the Russian defence ministry, who says that "all the missiles were destroyed."

The BBC is unable to independently verify the statement.

Russian attacks on Ukraine's eastern Donetsk region have killed three civilians and injured five more in the last 24 hours, the Reuters news agency reports, citing the regional head.

The area has seen some of the war's heaviest fighting, as Russian forces advance towards Pokrovsk, a city in the region.

The Russian defence ministry is also claiming its forces have taken control of Serhiivka, a village in the region, according to the the Russian state news agency, TASS.

Ukraine has ordered the evacuation of Pokrovsk, a city in the Donetsk Oblast, as Russian forces approach the region.

In a post on Telegram, the head of the city's military administration says it's important residents "don't delay" their evacuation, as Russian troops are "rapidly approaching the outskirts of Pokrovsk".

The city was the focus of the highest intensity of fighting between Ukrainian and Russian forces yesterday, according to the General Staff of the Armed Forces of Ukraine.

In a post on X, President Volodymyr Zelensky said the city was a key focus for defence forces, external, and was one of a number of areas "facing the most intense Russian assaults".

It's been 11 days since Ukrainian forces launched a surprise offensive on Russian soil with targeted attacks in border regions including Kursk, Belgorod and Bryansk.

Kyiv's incursion into mainland Russia comes two-and-a-half years after Moscow launched its full-scale invasion of Ukraine in February 2022.

Here's some images of life near the Sumy region in Ukraine, which borders the Kursk region in Russia.

Image source, Getty Images

Image source, Getty Images

Image source, Getty Images

Steve Rosenberg
Russia editor

Last night’s main news bulletin on Russian TV showed Russian troops in Kursk region trying to restore control.

“We’ll be victorious,” one soldier said.

“I’m 100% sure we’ll win,” declared another.

The soldiers had a signed photo of Vladimir Putin. The president’s portrait was also on their banner. If there’s a message here it is that president Putin will lead Russia to victory.

But in stark contrast to the typically triumphalist messages, a few days ago on state TV there was a rare, public moment of self-doubt. On a political talk show a film director suggested that “if there are more blunders like this one Russia might lose the war.”

“We must stop saying that everything in our country is fine,” Karen Shakhnazarov said. “There’s a lot that isn’t fine.”

He continued : “[On TV] we’re always showing Ukrainians who don’t want to fight. But now we can see: they’re fighting well. And they’re highly motivated. Why are we kidding ourselves?”

Steve Rosenberg
Russia editor

In the centre of Moscow I can see commuters rushing to a Metro station and people speeding by on electric scooters. It never ceases to amaze me how normal everything looks here on the surface.

In reality, there is nothing normal about what’s been happening in Russia for the last two-and-a-half years.

So many dramatic events: from Russia’s full-scale invasion of Ukraine to the Wagner mutiny. And now, the incursion by Ukrainian troops in Kursk region.

After talking to people on the streets of Moscow, it’s clear that the incursion has made the war feel closer.

“It makes me sad,” says Laura, “it shows our borders are unprotected.”

“Now I’m worried about World War Three,” Sophia tells me. “But I hope it’s just me worrying.”