Nick Thorpe
BBC Eastern Europe Correspondent

More than 4,000 people, mostly women and children, have so far fled across the border from Ukraine into Moldova. It’s not yet clear whether they intend stay there or cross into Romania.

One explanation for the high number of women and children is that the Ukrainian authorities are preventing the departure of men of military age, but there is no independent confirmation of that.

“We expect much larger numbers,” Roland Schilling, regional representative of the UN Refugee Agency, told the BBC from Chisinau.

“We are aware of large queues forming at border crossings. We are preparing our humanitarian response together with other UN agencies.”

The UN has previously warned that an invasion of Ukraine could trigger a large-scale refugee crisis.

Image source, Reuters

In the last few moments, Kyiv's Mayor Vitaliy Klitschko has announced a city-wide curfew.

"Friends! Kyiv is introducing a curfew from today. It will be in force between 22:00 and 07:00," he said.

"It is necessary for the safety of the capital's residents amid military aggression and with martial law in force," Klitschko added.

While public transport will be unavailable during the curfew, metro stations will remain open for use as shelters.

Our BBC Ukrainian team are covering the latest developments from the capital and elsewhere in Ukrainian here.

And you can find Russian-language updates from our colleagues here.

As Russian forces launch a major military assault on Ukraine, here are a selection of some of the most striking photos coming out of the region.

Image source, AFP

Image source, Getty Images

Image source, AFP

Image source, TASS via Getty Images

Image source, LA Times/Getty Images

Paul Adams
BBC diplomatic correspondent, in Kyiv

It’s clear that Russian paratroops have been in control of the Antonov airbase, around 15-20 miles outside Kyiv, since early this morning.

CNN has been reporting live from the scene, with paratroops clearly visible on the perimeter.

The Ukrainian national guard says it has launched a counter offensive. As Western intelligence officials predicted, this attack has progressed quickly, perhaps more quickly even than they expected.

Russian armoured columns have made rapid progress, south from the border with Belarus and north from the Crimean peninsula. What will the Russians do next?

Having established an operating base, the paratroops could now wait for the advancing Russian armour or use it to launch strikes into Kyiv. Either scenario could unfold soon.

Ukrainian MP Lesia Vasylenko has told BBC News “it’s a nightmare”.

“I could never even in my worst dreams imagine this kind of situation developing”.

She says it’s “surreal that we have to witness this in the middle of Europe in the 21st century”, adding “it’s unjust, it’s unfair, it’s clearly an invasion, it’s an attack on Ukraine”.

Vasylenko says at the moment Ukraine is doing all it can, “we are fighting back with all that we have”, she says.

But says she's afraid this will not be enough and she says, “we need the utmost support from all Western allies”.

She says they must come together “to stand for Ukraine, not just with more robust sanctions, but also with military presence here on the ground”.

Image source, AFP

Our colleagues from BBC Ukrainian in Kyiv are reporting that air-raid sirens are sounding in the centre of the city, as fears of potential Russian air strikes grow.

People have been advised to seek shelter and - as we've been reporting - many have taken refuge in metro stations.

"I woke up because of the sounds of bombing. I packed a bag and tried to escape," Maria Kashkoska told the AFP news agency earlier, as she sheltered within a station.

Earlier, midway through a broadcast, BBC correspondents Lyse Doucet and Clive Myrie put on flak jackets in the centre of the Ukrainian capital as sirens blared.

Image source, Murtaza Hameed

We've been hearing from people across Ukraine, bringing you their accounts of what's happening and how they're feeling.

Murtaza Hameed, a British medical student living in Kyiv, says he was “woken at half-five by an explosion”.

He says he lives about 40 minutes from Boryspil airport and has heard “explosions intermittently”.

"The sudden nature of [the attack] is the biggest shock," he says.

Although some people went to the shelters, he’s opted to stay in his apartment for now.

“I’ve picked up some supplies to last for the next few days – water, perishables and so on.”

He also says some people have asked him why he didn’t leave Kyiv earlier.

“As a student who’s been here four years, the Ukrainian people seemed very calm. My flight was booked for next week. Obviously that’s no longer an option. Logistically it’s very difficult to pack everything up and leave,” he says.

He told us his mother is in Islamabad and is “aware of the situation", adding: “she’s as calm as she can be.”

Image source, Getty Images

Former heavyweight boxing champion Vitali Klitschko, who’s now the Mayor of Kyiv, spoke to the BBC Radio 4's World at One earlier.

He says people were shocked to hear explosions in the city and is appealing for unity from the West to help Ukraine.

It's our goal, it’s our dream, to build a modern, democratic country and be "part of the European family", he says.

Klitschko says Russia’s army is one of the biggest in the world and he admits it will be a difficult fight, but he says Ukrainians don’t like Russian aggression and they will be "fighting for our future, fighting for our children”.

“I’m not scared about me, I’m a fighter”, he says - but he admits he is concerned about the three million people he's responsible for who live in Kyiv.

When asked what he would say to the Russian people? He replies every war brings blood, death and disability and questions if they need that along with sanctions.

Image source, AFP

It's an incredibly confused and fast-moving situation, but here's what we can tell you so far about what is happening on the ground.

Russian forces have invaded Ukraine from multiple directions, including from the separatist regions in the Donbas to the east, Belarus to the north and from occupied Crimea to the south.

Much of the fighting appears to be centred around the east.

Residents of Kharkiv, Ukraine's second largest city, say windows in apartment blocks were shaking from constant blasts as the Ukrainian military and Russian forces exchanged shellfire.

But clashes have have also been taking place around the capital Kyiv in the north and the Black Sea port cities of Odesa and Mariupol in the south.

Air strikes from Russia have been carried out on Ukrainian military bases and airports, with fierce fighting reported around a key airport near Kyiv.

The Ukrainian military claims to have shot down at least six Russian aircraft, while Russia claims to have destroyed more than 70 military targets in Ukraine.

Many Ukrainians are seeking shelter or trying to leave larger cities around the country, including thousands seen fleeing Kyiv.

Nick Eardley
Political correspondent

A source has said the meeting between the Foreign Secretary Liz Truss and the Russian ambassador Andre Kelin was “tempestuous”.

Truss summoned him to the Foreign Office this afternoon and ended the meeting early after telling the ambassador he should be ashamed of Russia’s behaviour in Ukraine.

The foreign secretary is understood to have said the Kremlin has lied repeatedly and its behaviour had made Russia an international pariah. The talks lasted around 10 minutes and Truss has now returned to talks with allies.

Image source, Getty Images

Russian Foreign Minister Sergei Lavrov says that Russia will always be ready for dialogue despite Russian forces launching a major military assault on Ukraine.

"Unfortunately, our Western friends do not respect international law, trying to destroy it and promote what they call 'rules-based order,'" Lavrov says, state-owned news agency RIA Novosti reports.

"We had intensive and detailed discussions with our American colleagues, with other Nato members," he says.

We hope that there is still a chance to return to international law and international obligations."

Lavrov says that Russia will "always be ready for a dialogue that will return us to justice and the principles of the UN charter".

What could the Russian military plan be?published at 14:51 Greenwich Mean Time 24 February 2022

14:51 GMT 24 February 2022

Jonathan Marcus
Exeter University

Image source, Getty Images

This Russian operation goes way beyond securing or even expanding the pro-Moscow separatist-controlled areas in eastern Ukraine.

Vladimir Putin’s stated goal is the “demilitarisation" and "denazification" of Ukraine (In response, President Zelensky, who is Jewish, asked: "How could I be a Nazi?"). Those goals may well translate into defeating the Ukrainian military and imposing a government willing to do Moscow’s bidding.

While initial attacks have come from the air and missiles, Russia’s real strength is its ground forces - heavy armour, mechanised units and above all artillery and rockets.

Initial attacks against airfields, logistics centres and probably air defence and command centres are being swiftly followed up by ground advances into Ukraine from the north, from Crimea in the south and from the eastern separatist enclaves in the Donbas.

Their objectives may well be to isolate the Ukrainian capital Kyiv and to cut off and destroy Ukrainian forces in the east of the country.

Attacks against airports in Ukraine may in part be an effort to deter and prevent any further Western arms shipments into the country.

Meanwhile Russian exercises in Transnistria - a separatist area of Moldova, which borders Ukraine and Romania - raise concerns that Russia might be seeking to complete other “unfinished business".

Modern mechanised combat is fast-paced, brutal and extraordinarily destructive. Europe has not seen fighting like this since 1945.

We've got more from French President Emmanuel Macron who says his country will hit Russia with sanctions of the same level of aggression as the country is guilty of.

He says Russia could expect tough sanctions that would hit its military, its economy and its energy sector.

"We will back Ukraine without hesitation, and we will take our responsibility to protect the sovereignty and the security of our European allies.”

"The events of last night mark a turning point in the history of Europe," said Macron in a televised address to the French nation, standing before French, European Union and Ukrainian flags.

"We will respond to this act of war without weakness, with calm, determination and unity," he added.

Image source, Unknown

A video of a Russian military helicopter downed during fighting at Hostomel airport, near Kyiv, has been verified by the BBC, however the source of the video is unknown.

Ukrainian commander in chief Lieutenant General Valerii Zaluzhnyi has confirmed the military is fighting Russian forces for control of the airport in the Kyiv region, the Reuters news agency reports.

Hostomel is Ukraine's most important international cargo airport, as well as a key military airbase.

It is also the base of the world's largest cargo plane - the Mriya.

Shayan Sardarizadeh
BBC Monitoring

Image source, Twitter

Soon after President Putin declared the beginning of the invasion of Ukraine, videos and images claiming to be from the conflict began trending on major social networks.

While there is lots of genuine footage, some viral clips racking up hundreds of thousands of views show events from past conflicts or old military exercises. Many of these seem to coming from users posting content without checking.

The BBC has seen videos of the 2014 Russia-Ukraine war, the 2011 Libyan war and the 2020 Beirut explosions going viral.

In one example, a former Ukrainian ambassador to the US tweeted a video which he claimed was taken in Mariupol, but a version of the same clip was uploaded to TikTok weeks ago and apparently showing a lightning hitting a power station.

Another viral video claiming to show Russian military paratroopers landing in Ukraine first appeared online in 2016.

But Twitter seems to be taking a proactive role in confronting misleading content, as it seemed to have removed several videos proven to be old or false by fact-checkers and researchers.

Marta Shokalo
Editor BBC Ukrainian Service, Kyiv

Image source, Marta Shokalo

I was awake at night when I got a message from a colleague about Vladimir Putin's speech announcing an invasion.

Then immediately the explosions began. I could hear them from my home, and people in different parts of the city started sending messages to our WhatsApp group, about explosions happening close to them.

To realise that Kyiv itself was under attack, not the front line in the east of the country, was a big shock.

There is no safe place in Ukraine any more.

The biggest fear for ordinary people here is running out of electricity and the internet not working - then we would be really isolated.

There is an air of panic, now that we know the entire country is under attack.

Read Marta's full account here

Image source, Reuters

If you’re just joining us, we’re working to keep you up to date with the fast-moving events in Ukraine. Here’s the latest we know about the Russian invasion:

Military action

Russian forces have invaded Ukraine, with missile strikes and explosions reported near major cities and on its military infrastructure.

The Ukrainian military says it has killed about 50 Russian "occupiers" and shot down at least six Russian aircraft, although this has not been independently verified.

On its side, Russia claims it has met little resistance and claims that Ukrainian armed forces are fleeing en masse, abandoning their weapons and positions.

Civilian impact

Emergency sirens have been sounding in Kyiv since the first explosions in the early hours. Huge traffic jams have built up as residents try to flee the city after Ukraine closed its airspace to civilian flights.

Elsewhere, residents are seeking shelter in stations - and queues have formed for buses, cashpoints and petrol.

Several European countries bordering Ukraine, including Poland, Slovakia and Hungary, say they are preparing for an influx of refugees.

Image source, Reuters

International condemnation

Neighbouring countries have been reacting to the crisis.

The prime minister of the Baltic republic of Estonia, bordering Russia, said a number of Nato allies that shared borders with Russia had agreed to launch consultations , externalunder Nato's Article 4.

Moldova has declared a state of emergency and is prepared to give help to tens of thousands of Ukrainians. Lithuanian President Gitanas Nauseda also said he was signing a state of emergency to be approved by parliament.

Nato secretary general Jens Stoltenberg said: "We will continue to do whatever is necessary to shield the alliance from aggression."

The US, EU, UK and Japan have imposed sanctions against leading Russians, Russian banks and MPs who backed the move. UK Prime Minister Boris Johnson said in a TV address the "hideous and barbaric venture by Vladimir Putin must end in failure".

Nick Eardley
Political correspondent

Senior ministers in London are spending the next few hours speaking to their counterparts in G7 capitals.

The government intends to announce what is says is a severe sanctions package later this afternoon – when the prime minister addresses Parliament. The government wants that to be done in line with allies.

After criticism the initial sanctions package did not go far enough, ministers made clear they had more waiting to be used at the right time.

It’s likely that will involve travel bans and asset freezes on more individuals and sanctions on more banks. It could also extend to key Russian industries like technology, energy and chemicals.

Ministers have also been discussing ways to restrict Russian access to UK financial systems. Labour wants Russia banned from Swift system for international payments.

The UK is also planning to provide military assistance to Ukraine – but that won’t involve boots on the grounds.

US President Joe Biden has called a meeting of the US's National Security Council to discuss Ukraine, a White House Official says.

Jon Donnison
BBC News, at Westminster

Image source, PA Media

Waving the country's blue and yellow national flag and chanting anti-Russia slogans, several hundred pro-Ukraine supporters are gathered on Whitehall in front of Downing Street.

Some are carrying placards with depictions of Vladimir Putin alongside the words "terrorist" and "murderer."

The crowd went silent while Ukraine's national anthem was played before erupting into applause and resuming a chant of "Stop Putin. Stop the war."

Olga Smith, a musician, artist and teacher, moved to London from Ukraine five years ago. Her daughter is still there, along with her four grandchildren.

Olga said her daughter called her in the early hours to say the invasion had begun and that their region was being bombed.

But Olga says this didn't all start today.

"It's been going on for eight years." she said. "The West needs to do more to stop Putin now, because if they don't he wont stop here. He will want to expand into more and more territory."

Image source, PA Media

Image source, PA Media