Ukraine's ambassador to the UK, Vadym Prystaiko, tells the BBC that Kyiv cannot confirm that Russia is withdrawing its troops.

"Sometimes their forces are being pulled out, some new forces are being brought back.

"Some mobile [pontoon] bridges have been built over a river [in Belarus] just six kilometres from the Ukrainian border. So, these preparations are very worrying for us," Prystaiko says.

He says that right now Russia had about 130,000 troops on Ukraine's borders.

And when asked about the current numbers of Ukrainian troops, the ambassador answers: "We have enough forces right now - it's around 250,000 in the Ukrainian army.

"We raised it by another 100,000 troops; we have 300,000 people signed up for territorial defence units; and we have reservists of up to 1.62 million people who want to defend our nation."

Prystaiko adds Ukrainians "will fight ourselves if we need to", not "leaving this to Nato or anyone else". But he stresses that Ukraine needs "some equipment to defend ourselves".

Image source, Reuters

The situation near Russia's border with Ukraine could ignite at any time, a Kremlin spokesperson says.

"Any moment [the situation] risks moving from the area of information attacks to consequences that will cause a new flare-up of war in close proximity to our borders," spokesperson Dmitry Peskov tells journalists.

The Kremlin says it is deeply concerned by reports of violence in Ukraine's rebel-held Donbas region and is closely monitoring the situation.

The official repeated Moscow's claim that some Russian troops were being withdrawn from the border region, but says the process would take some time.

He also dismissed reports that Russia is planning an invasion of Ukraine, something Moscow has repeatedly denied in recent weeks.

US Secretary of Defence Lloyd Austin is also in Brussels, he says if there is a war, then Vladimir Putin will bear the responsibility for the suffering and sacrifice that ensues.

He says the US and its allies are staying vigilant and are increasing readiness.

A peaceful outcome "respecting Ukraine's sovereignty and territorial integrity represents the best outcome" - both for Ukraine and Russia, and its people, Austin says.

If Putin is serious about reaching that kind of resolution then he will find "no better or more serious interlocutor" than the US and Nato.

But if he's not, then "it will be clear to the entire world that he started a war with diplomatic options left on the table", the retired army general adds.

There is "nothing inevitable" about the looming conflict and it can still be averted, he stresses. The path to diplomacy may be difficult but is worth the trek, he says.

Image source, EPA

More now from Nato's Secretary General Jens Stoltenberg, who has been defending the right of nations such as Ukraine to seek membership of the alliance - something strongly opposed by Russia.

"We cannot accept a return to the age of spheres of influence where big powers bully, intimidate or dictate to others," he tells the press conference.

Stoltenberg also says Nato is considering sending "battle groups" to Romania and elsewhere in the south-east of the alliance's territory.

“Nato has to respond when we see aggressive actions by Russia," he says, while calling for dialogue and de-escalation from Moscow.

As we mentioned earlier, Liz Truss has landed in Ukraine.

Shortly after arriving, the UK foreign secretary tweeted that she was "very concerned" about reports of "increased Russian aggression" today.

Those include 7,000 extra Russian troops reported to have been sent to the Ukraine border and reports of an attack by pro-Russia forces on a Ukrainian nursery.

Truss wrote that the UK "calls on Russia to withdraw its troops - there is still time for diplomacy and de-escalation".

And she said Russia was attempting to fabricate a pretext to invade Ukraine with "reports of alleged abnormal military activity by Ukraine in Donbas".

"This is straight out of the Kremlin playbook," she added.

The UK "will continue to call out Russia’s disinformation campaign", she wrote.

We're hearing from Nato's Secretary General Jens Stoltenberg, he says Russia might use a false-flag attack to justify using force against Ukraine.

"We are concerned that Russia is trying to stage a pretext for an armed attack against Ukraine," he tells a press conference in Brussels.

"Russia has amassed the biggest force we've seen in Europe for decades in and around Ukraine. There are many Russian intelligence officers stationed in Ukraine. We have seen attempts to stage pretext, false-flag operations to provide an excuse for invading Ukraine."

A false-flag attack is where one side stages or fabricates an attack against it in order to justify the use of force in retaliation.

"We continue to call on Russia to de-escalate, withdraw forces, and engage in dialogue," Stoltenberg adds.

Ukraine wants to join Nato - but knows it won't happen yetpublished at 12:29 Greenwich Mean Time 17 February 2022

12:29 GMT 17 February 2022

Paul Adams
BBC diplomatic correspondent

President Volodymyr Zelensky wants one thing to be abundantly clear: Ukraine sees Nato membership as the key to his country’s long term security.

He is not about to give up on this cherished ambition.

But he also recognises that it’s not about to happen now. Accession is a lengthy process and Ukraine hasn’t even started.

In the meantime, with Russian forces still menacing his country, he knows that Nato cannot spring to Ukraine’s defence the way it would for one of its members.

The best he can hope for is more of the diplomatic and military support he’s been getting in recent weeks.

Jessica Parker
BBC political correspondent

EU leaders are meeting now to discuss the latest situation with Ukraine and Russia.

They were already in Brussels for an EU-Africa summit, but there was a last-minute decision to hold a special, hour-long, discussion before that summit got underway.

Diplomatic sources suggest that the EU’s sanctions package will not be expressly "presented" to leaders today. Rather there will be an "overview" of the current situation.

While the European Commission is deliberately tight-lipped about its sanctions plans, officials are clear that it would be a ‘reactive’ set of measures; meaning the level of sanctions would depend on the level of any incursion by Russia.

Liz Truss, the UK's foreign secretary, has just arrived in Ukraine.

She's due to give a speech in Kyiv later.

UK ambassador to Ukraine Melinda Simmons confirmed she'd arrived by posting a picture to Twitter of an RAF transport plane touching down."

Truss said ahead of her visit that the West "must not be lulled into a false sense of security" after Russia claimed it had pulled back troops from the border with Ukraine.

Writing in the Daily Telegraph, she said there was "currently no evidence" Russia was withdrawing.

Image source, Getty Images

Here's a recap of where we are at so far today, if you're just joining us.

• Ukraine's President Volodymyr Zelensky says joining the Nato alliance is a guarantee of security for his country - and that he will not compromise on this
• He tells the BBC: "It's not an ambition. It's our life."
• Russia is opposed to Ukraine ever joining and wants guarantees that this will not happen
• The US and Western allies are warning Russian forces could launch military action any day - but the Kremlin has repeatedly said there are no such plans and claims some units have been withdrawn in recent days
• The world is watching for proof of Russian de-escalation - as a senior US official says contrary to this claim, a further 7,000 troops have arrived at Ukraine's borders
• President of the European Commission Ursula von der Leyen says the EU will remain vigilant until Moscow's words are reflected on the ground

• UK Foreign Secretary Liz Truss, who is travelling to Ukraine, says the West should not be fooled by Russia's claims

More than 100,000 Russian troops have been positioned within reach of Ukraine's borders as Moscow demands security guarantees from the West.

While the US and its Western allies warn that Russian forces are ready to launch military action any day, the Kremlin has repeatedly said it has no such plans and points to the withdrawal of some units in recent days.

What happens next could jeopardise Europe's entire security structure - here's our explainer on this complicated and fast-moving story.

Image source, EPA

Here's a bit more from Russia's Foreign Minister Sergei Lavrov, who has been speaking in Moscow, responding to a statement from Nato announcing it's deploying additional forces.

He says by deploying troops, Nato is "doing exactly the same thing that it accuses us of doing", describing the alliance as having crossed the line.

Lavrov continues: "But of course the spiciest part of the statement is the very beginning: 'We are gravely concerned by the very large scale, unprovoked and unjustified Russian military build-up in and around Ukraine and in Belarus.'

"What do you think about that? You know, this sense of personal superiority and personal infallibility has in my opinion already crossed the line, and unfortunately, our Nato colleagues simply cannot see this line."

Image source, Ukraine's Joint Forces Operation

As we've been reporting, Ukrainian officials have accused Russia-backed separatists in Donbas of shelling a village on the Ukraine-controlled area.

"The Russian occupation forces shelled the town of Stanytsia Luhanska in the Luhansk region, crudely violating the ceasefire agreement", the Ukrainian military officials said in a statement.

As a result of the strike the building of a village kindergarten was hit - a shell smashed through the wall of a music room.

Image source, Ukraine's Joint Forces Operation

Village head Albert Zinchenko told BBC News Ukraine three people were injured.

"A security guard, a laundry worker and an assistant nursery school teacher. They are in hospital suffering from shell-shock and stress," said the mayor.

The mayor added that some children were in the building at the time of the shelling but escaped unharmed.

Earlier, Russia-backed separatists in the Donbas region claimed the Ukrainian military started shelling a number of settlements.

Image source, Reuters

Defence Secretary Ben Wallace says Russia will be judged by its actions as troop build-up continues.

"We've seen the opposite of some of the statements", he says. "We've seen increase of troops over the last 48 hours up to 7,000, we've seen a bridge constructed from Belarus into Ukraine - or near Ukraine.

"I think we'll take them by their word, but we're going to judge Russia by their actions and at the moment the troops build-up continues."

Wallace says Nato, the alliance of Western governments, is united and is "deadly serious on how we're going to face the threat being posed to Ukraine and potentially our security".

Speaking after a meeting of defence ministers, he says it's becoming "tragically normal" for Russia to use "malign activity and threats to try and get its way" and Europe has to respond to that.

"This is a real challenge to the stability of Europe," Wallace adds.

Russian Foreign Minister Sergei Lavrov says Moscow will send a formal response to the US on the issue of security guarantees on Ukraine.

Lavrov says it will be sent on paper and electronically and will be made available in a matter of hours - adding it was necessary to make it public.

Russia is demanding that Ukraine should not be allowed to join Nato - but Washington and Brussels have so far refused to promise that.

More strong comments from Ukrainian President Volodymyr Zelensky.

Admitting that a path to joining Nato and the EU would be "long", he stresses that "for me as president the most important thing on this path is not to lose my country.

"Nato is a guarantee of security. So how can we choose any other path? For us it’s a guarantee of not losing our independence."

Asked by the BBC's Sarah Rainsford about pressure from some European nations who also wanted to keep Ukraine out of Nato, Zelensky answers: "We can’t close our eyes… and say it’s only Russia that doesn’t want us there. It’s not true."

The president also rules out any national referendum on Nato membership, saying Ukraine's desire to be a member is already written in the country's constitution.

Zelensky also accuses Russia of whipping up a crisis over the Nato membership issue "to justify being at the border... that they are supposedly protecting their sovereignty… that’s all distorted information.

He adds "some EU countries play along with Russia… which is wrong."

Here's a profile of the Ukrainian president.

Ukrainian President Volodymyr Zelensky has reiterated his determination for his country to join Nato, saying there is "no other path" for Ukraine. But what is Nato?

Nato - the North Atlantic Treaty Organisation - is the world's most powerful regional defence alliance.

Its 30 members - which include the UK, US, Canada, France and three former Soviet republics - agree to come to one another's aid in the event of an armed attack against any one member state.

Ukraine is not a member of Nato. But, it is a "partner country" and may be allowed to join the alliance sometime in the future.

Russia sees this potential partnership as a direct threat to its security and wants assurances from Western powers that this will never happen.

But the US is refusing to bar Ukraine from Nato, saying that as a sovereign nation it should be free to decide on its own security alliances. Read more here.

Ukrainian President Volodymyr Zelensky has said that Nato membership is a "guarantee of security" for the country, ruling out any compromises.

Asked by the BBC's Sarah Rainsford whether Kyiv was ready to give up its ambition of joining the Western military alliance, Zelensky answered: "It’s not Ukraine’s ‘ambition’. We lost 15,000 people. It’s not an ambition. It’s our life.

"It’s not about Nato. It’s about the future of the people... The question about Nato is not about membership. If we speak about Nato, the EU, the temporarily occupied territories - we are speaking about our independence. That’s it. That we decided what we want and will do in our future."

Russia has been pressing Nato and the US to rule out any potential Ukraine membership of the alliance, threatening "military-technical measures" if its demand is not satisfied.

The President of the European Commission says until Moscow's words are reflected by action on the ground the EU shall remain vigilant.

Ursula von der Leyen says "we hear claims from Russia about pulling back troops, but we have not seen any signs so far of de-escalation on the ground."

"To the contrary, we see that the build-up continues," von der Leyen adds.

Her comments, made before a meeting with Czech Prime Minister Petr Fiala, echo similar concerns voiced by the US and UK that Russia is continuing to deploy troops to the border region.

The EU chief says she believes there is still a path to a diplomatic solution with Moscow, but until then "we will not let our guard down."

"We hope for the best, but we are prepared for the worst," she says.

Image source, Reuters

More on that news of the reported fighting in eastern Ukraine we brought you earlier.

The Ukrainian military says a kindergarten in Stanysia Luhanska was hit after the rebels used heavy artillery.

It also says half of the town is now without electricity after its communal infrastructure was damaged.