Nato chief Jens Stoltenberg says the alliance has not seen any de-escalation of Russian military build-up on Ukraine's borders
Following a meeting of Nato defence ministers in Brussels, he says the security threat from Russia represents a "new normal" for Europe
"This is the biggest concentration in forces in Europe since the Cold War," he says
It comes after Russia said it was pulling back more troops - this time from the Crimean peninsula
A series of cyber attacks on Tuesday knocked out the websites of Ukraine's defence ministry and two banks
Ukraine has been marking a day of unity after earlier US reports suggested Russia could attack today
Nato secretary general Jens Stoltenberg begins the news conference by saying defence ministers have met to discuss the "continued" troop build up on the borders of Ukraine.
He says allies welcome all diplomatic efforts and says there are signs from Moscow that diplomacy could win through.
But he says there are no signs of de-escalation or withdrawal of Russian troops.
And, after a slight delay, here's Secretary General Jens Stoltenberg to begin the Nato news conference in Brussels.
Paul Adams
BBC diplomatic correspondent
The scepticism from Ukrainian President Zelensky and his Western allies about a supposed Russian withdrawal is understandable.
Russian defence ministry pictures showing military movements, released for public consumption, don’t really tell us anything.
As Jens Stoltenberg says, Russian troops come and go all the time. And Moscow always said that units would return to base after its planned exercises were over.
But the fact remains that Russian forces capable of launching an invasion at short notice remain in place, to Ukraine’s north, east and south.
Western nations will be looking for their own verifiable evidence of withdrawal on a much bigger scale, not carefully curated video handouts from Moscow.
American surveillance aircraft will be gathering vital intelligence and commercial satellite companies will be looking to see what, if anything, has changed on the ground.
Some of that material will probably become available in the coming days. Only then will we get a clearer idea whether any kind of significant withdrawal is taking place.
Almost half an hour later than planned, Nato defence ministers are taking their "family photo" - the classic line-up for the media and the historical record.
The press conference should follow shortly.
Image source, Getty ImagesIt looks like the Nato news conference is delayed, so while we wait let's take a quick look at how we got here.
Members of Nato have been weighing up how far they should go to help Ukraine, in the face of a possible Russian invasion.
The 30-country alliance has been stepping up its military readiness and aid to Ukraine.
Meanwhile, Russia has been pushing for assurances from Western powers that Ukraine will never join the alliance.
The former Soviet republic is not a Nato member, but it is a "partner country" - which means it may be allowed to join the alliance sometime in the future.
We're expecting to hear from Nato chief Jens Stoltenberg at a press conference shortly, following a meeting of defence ministers in Brussels.
We'll bring you all the latest lines, after the secretary general said the alliance would "continue to work for the best.. while preparing for the worst" on the Ukraine crisis.
Despite widespread scepticism, Russia's defence ministry insists it is pulling back from the border.
Tanks have been filmed being loaded onto trains in footage released by Russia's defence ministry.
Officials said the tanks were being transported away from the border with Ukraine to their permanent bases after undertaking drills.
Image source, Getty ImagesEchoing comments from Nato Secretary General Jens Stoltenberg, US Secretary of State Antony Blinken says there hasn't been any "meaningful pullback" of Russian forces from Ukraine's border - despite Russia's claims.
"There's a difference between what Russia says and what it does," he tells ABC News.
"On the contrary, we continue to see forces, especially forces in the vanguard of any renewed aggression against Ukraine, continuing to be at the border, to mass at the border."
And he says Russia could still act on "very short notice". Vladimir Putin could "pull the trigger" today or tomorrow if he wanted to, he says.
Image source, ReutersIn his opening remarks at a meeting of Nato defence ministers, Secretary General Jens Stoltenberg describes the current situation as "a dangerous moment for European security".
"Russia has amassed an invasion force on the borders of Ukraine; at the same time there are signs from Moscow that diplomacy should continue - this gives grounds for cautious optimism," he says.
The secretary general cautioned there had been no sign of de-escalation on the ground.
He reiterates that Nato "is not a threat to Russia" and that the military alliance remains ready to talk "and find a diplomatic way forward".
But he adds: "While we continue to work for the best, we must also be prepared for the worst.
"We will do what is necessary to protect and defend all allies."
Jonathan Beale
BBC defence correspondent, in Brussels
Image source, ReutersClaims by Russia that it has withdrawn some of its forces from the border have been met by deep scepticism from Nato allies.
Nato’s secretary general, Jens Stoltenberg, said so far the alliance had not seen any evidence of a Russian de-escalation. On the contrary, he said Russia appeared to be continuing its military build-up.
A senior Western intelligence official told the BBC that Russia’s words now needed to be matched by actions: "We’re at the point where the loaded gun needs to be holstered."
Nato says Russia still has forces in place to carry out a full-scale invasion if that is what President Putin decides.
There’s also concern that this crisis is far from over - with Russia maintaining an increased military presence over the longer term.
Over the past year, each time Russia claimed it was drawing down forces they’d only been "reset at a higher level" - with troops leaving military equipment behind and then returning, the official told the BBC.
Defence ministers in Brussels are now discussing beefing up their own longer term military posture, while maintaining a strategy of deterrence and dialogue - with the hope that Russia engages in serious talks.
But there’s still the question as to whether those talks could lead to a peaceful outcome.
Viktoriia Zhuhan
BBC Ukrainian in Kyiv
Image source, Getty ImagesThe Ukrainian flag has been raised across the country, to mark Unity Day
Dressed in embroidered national shirts, children and teachers sing the national anthem and line up for a group photo. They are following official instructions on how to celebrate what's being billed as a new "day of unity" in Ukraine.
"I have mixed emotions. My first reaction was that this feels artificially imposed," says Victoria Zabuzova, 36, as she picks up her eight-year-old son from school.
"On the other hand, the tension is almost palpable - so maybe, this wasn’t the worst way to wind down."
She is one of many parents who recently received two contrasting messages from the government - one carried instructions on how to dress children for the celebrations, and the other an update on the state of the bomb shelter their school or kindergarden might use.
But even though the overnight invasion - which reports from US intelligence suggested could take place - didn't materialise, the threats are far from gone.
Sarah Rainsford
BBC Eastern Europe Correspondent
President Zelensky is taking part in a "unity day" tour of the country
The recent troop build-up by Russia has brought a long-building stand-off between Moscow and the West to a dangerous peak, trapping Ukraine in the middle.
For Kyiv, though, President Volodymyr Zelensky has stressed the Russian threat "didn’t start yesterday". So his country, he said, remained calm.
Zelensky flew into a military training ground near Rivne in Western Ukraine by helicopter to watch forces simulate repelling a major cross-border attack on their country.
When I asked whether he thought the Russian threat had receded, he said he had "only heard about it".
"When the troops do pull back, everyone will see that," he told me. "But for now, it’s just statements."
On the mock-battlefield before him, Ukraine’s troops fought off the supposed aggressor, pushing back in a flurry of gunfire and explosions – testing some of the weaponry delivered by allies including the US, Britain and the Baltics.
It all played out some 80 kilometres from the border with Belarus, where Russia has also deployed troops and tanks for the countries’ own joint exercises.
So, an instructor stressed, the Ukrainians were aiming their guns in the opposite direction, to be sure they don’t spark a real-life attack in response.
It's been a busy week of news. If you're in need of a quick catch-up on what's going on with Russia and Ukraine - here's a primer.
Big picture: Russia has been massing troops on Ukraine's borders for months, raising fears that it wants to invade. A key question now is if Russia really plans to meaningfully pull back its forces or if Ukrainians will continue to live with the threat of a new war hanging over them.
The context: Russia is adamant it has no plans to attack Ukraine, but the threat is being taken seriously because Russia invaded Ukraine in 2014 and seized its territory. It has also backed rebels fighting the Ukrainian military in a long-running conflict in the east.
No to Nato: Russia wants assurances that Ukraine will not be able to join the Nato defence alliance. Nato members, including the UK, pledge that an attack on any of them is an attack on all of them. The issue of countries near and neighbouring Russia joining Nato is a very sensitive one for Vladimir Putin.
De-escalation: Nato has called for Russia to withdraw troops and de-escalate the situation. Russia says it is doing this but Ukraine's president said earlier today: "We don't see any withdrawal yet".
Image source, RUSSIAN DEFENSE MINISTRY / HANDOUTRussia says it is pulling back some of its troops
Russian officials have been mocking the West over warnings that Moscow could launch an invasion of Ukraine on 16 February - that's today, if you've not looked at your calendar.
Ukraine declared a "day of unity" after the date was suggested by US officials and widely reported.
"I'd like to ask if US and British sources of disinformation... could publish the schedule of our upcoming invasions for the year. I'd like to plan my holidays," Russian Foreign Ministry spokeswoman Maria Zakharova wrote in a Facebook post.
Russia's envoy to the European Union, Vladimir Chizhov, meanwhile said wars in Europe "rarely start on Wednesdays".
"This may not be a strong enough guarantee, but I can assure you that, as far as Russia is concerned, there will be no attack this coming Wednesday," he added. "Nor will there be any escalation next week or the week after, or next month."
Russia's deputy ambassador to the United Nations, Dmitry Polyanskiy, is reported to have quipped that Western leaders should see a doctor for their "paranoia".
Russia has announced that it is pulling troops back from Ukraine's border but Nato - the western military alliance - says it doesn't see any "de-escalation" on the ground, and that in fact, Russia is continuing its military build-up.
Image source, Getty ImagesThe UK has warned it would introduce tough sanctions on Russia if it invaded Ukraine, with Moscow responding that it would retaliate to such a move.
But there have also been calls for a crackdown specifically targeting illicit Russian money in the UK.
Anti-corruption organisation Transparency International has identified more than £5bn of property bought in the UK with what it says is "suspicious wealth", one-fifth of which has come from Russia.
A Home Office report says the UK has seen "a significant volume of Russian, or Russian-linked illicit finance", which is spent on things like luxury property, cars and school fees, and sometimes as donations to cultural institutions, which allow individuals to "launder their reputation".
In 2018, the UK government introduced a mechanism to confiscate property without first seeking a criminal conviction, but these unexplained wealth orders have only been used four times - with only one resulting in the confiscation of property.
Here - our Reality Check team take a look at how much Russian money there could be in the UK.
Image source, PA MediaThe leader of the opposition party in the UK says it is "very important that we stand united with our allies, united with Nato" against "Russian aggression".
Labour leader Keir Starmer adds that he wants to see the government go further with sanctions.
"I don't think they've used the powers they've already got as much as they should have done and I don't think they've looked closely enough at their own donations," he says.
"I want to see further sanctions put in place as quickly as possible."
The UK government has already introduced new powers to expand sanctions against Russian individuals and businesses if the country invades Ukraine.
Svyatoslav Khomenko
BBC Russian in Kharkiv
A mild winter day in Ukraine’s second city started with the raising of the national blue-and-yellow flag and a performance of the national anthem by a choir from the Kharkiv Opera.
Dozens of people gathered in the centre of the city - this show of patriotism is especially poignant here, just 40km (25 miles) from the Russian border.
This is a follow-up to President Zelensky’s decision to turn the narrative around and instead of fearing an invasion on 16 February - leaked to some media as a possible date for a Russian incursion into Ukraine - encourage people to come out with flags and blue-and-yellow ribbons pinned to their coats to show strength and unity of Ukrainians.
While this is not a public holiday, hundreds of people across the country gathered in central squares of cities, towns and villages. School children across Ukraine were encouraged to don traditional embroidered shirts - Ukrainian "vyshyvanka".
There have been some sceptical voices on social media who compared this state-sponsored show of patriotism to the Communist era. Others believe this is an important boost of morale for Ukraine at tough times.
Moscow wants Nato to publicly state that it will not let Ukraine join the defensive alliance, Russian diplomat Konstantin Gavrilov says.
"Russia will insist that Nato publicly announces its refusal to accept Ukraine into its ranks. Kyiv, in turn, must proclaim its neutral, non-aligned status”, he says, according to Russia’s Ria news agency.
Gavrilov's comments came as Nato defence ministers began a two-day meeting in Brussels.
Russia has repeatedly called for assurances from Western powers that Ukraine will not be allowed to join - but Nato says that as a sovereign nation Ukraine should be free to decide its own security alliances.
Ukraine is currently a "partner country", which means there is an understanding that it may be allowed to join Nato sometime in the future.
But Russian President Vladimir Putin claims Western powers are using the alliance to surround Russia, and he wants Nato to cease its military activities in eastern Europe.
Earlier, John Sawers, the former head of UK security agency MI6, told BBC Radio 4's Today programme there was "no prospect" of Ukraine actually joining Nato as it would have been bringing into the alliance an existing conflict between Russia and Ukraine.
But he said that you could not turn Ukraine down "on the basis that Russia has vetoed it".
Ukraine was never going to join Nato, says ex-MI6 chief
Former head of the British army Richard Dannatt says President Putin has succeeded in making it less likely Ukraine will join Nato - but in the process has brought other members of the alliance closer together.
"I believe he has achieved something and that is the distancing of the likelihood of Ukraine joining Nato," he tells the BBC.
But while the Russian president hoped to see "disharmony" among the Nato allies, instead Dannatt says he has united them.
Dannatt says he thinks Ukraine should not join the Western military alliance as it would be a "provocation too far" but that we should support an independent Ukraine.
He adds that he does not think Russia will invade Ukraine, saying "it's just not a realistic or right thing to do for a supposedly civilised country like Russia".
You can read more about why Russia doesn't want Ukraine to join Nato here.