The UK is waking up to the news that Vladimir Putin has finally declared war on Ukraine.
In a live TV address on Russian state TV, Putin announced he was launching a “special military operation” in the east of the country.
The move comes despite frantic diplomatic efforts to avoid full-scale conflict in recent days.
Here is everything we know so far as western leaders try to co-ordinate their response to the unfolding crisis.
What has Putin announced?
In a now-familiar broadcast from his desk at the Kremlin, flanked by Russian flags and surrounded by 1980s-era telephones, Putin said his goal was the “demilitarisation” of Ukraine.
Despite the fact that the military action is unprovoked, Putin said the responsibility for any bloodshed would lie with the Ukrainian “regime”.
In a warning to the west, he said any attempt to interfere with the Russian assault would lead to “consequences they have never seen”.
Putin went on to accuse the US and its allies of ignoring Russia’s demand to prevent Ukraine from joining Nato and offer Moscow security guarantees.
All Ukrainian servicemen who lay down arms will be able to safely leave the zone of combat, Putin said.
What is happening in Ukraine?
Explosions could be heard in the capital city of Kyiv shortly after Putin’s address, while explosions were also reported in the cities of Odesa and Kharkiv.
Ukraine’s border guard agency said the Russian military attacked the country from neighbouring Belarus.
The agency said that the Russian troops unleashed an artillery barrage as part of an attack backed by Belarus. They said the Ukrainian border guards were firing back, adding that there was no immediate report of casualties.
News correspondents in Kyiv were interrupted by the sounds of explosions in or near the Ukrainian capital before dawn on Thursday, less than an hour after Putin’s announcement.
Reporting from a hotel rooftop in central Kyiv, CNN senior international correspondent Matthew Chance said he could hear loud booms in the distance.
The Ukrainian interior ministry said that rocket attacks had begun targeting Ukrainian fighter jets at an airport outside Kyiv, The New York Times reported. The country’s state emergency service reported attacks against 10 Ukrainian regions, primarily in the east and south. The government agency said several planes had been hit and information about shootings was coming in constantly.
How has the UK government responded?
Boris Johnson has already spoken to Ukrainian president Volodymyr Zelenskyy this morning.
Downing Street said the prime minister had said the West would not stand by as President Putin waged his campaign against the Ukrainian people.
In a tweet, Johnson said Putin has “chosen a path of bloodshed and destruction” and that the UK and its allies would “respond decisively”.
Defence secretary Ben Wallace - who claimed on Wednesday that Putin had “gone full tonto” - described Russia’s actions as “naked aggression against a democratic country” and said no one had been fooled by the Kremlin’s “false flags and fake narratives”.
He said: “No one should forget this day. Putin thinks this land grab is about securing his legacy – it will be, but not the one that he wishes.”
Foreign secretary Liz Truss tweeted: “I strongly condemn the appalling, unprovoked attack President Putin has launched on the people of Ukraine.
“We stand with Ukraine and we will work with our international partners to respond to this terrible act of (aggression).”
Meanwhile, Labour leader Keir Starmer said: “Vladimir Putin’s attack on Ukraine is unprovoked and unjustifiable. His actions will have horrendous and tragic consequences that will echo throughout the world and throughout history.
“All those who believe in the triumph of democracy over dictatorship, good over evil, freedom over the jackboot of tyranny must now support the Ukrainian people.”
What has been the international response?
In a statement, US president Joe Biden said: “The prayers of the entire world are with the people of Ukraine tonight as they suffer an unprovoked and unjustified attack by Russian military forces.
“President Putin has chosen a premeditated war that will bring a catastrophic loss of life and human suffering. Russia alone is responsible for the death and destruction this attack will bring, and the United States and its allies and partners will respond in a united and decisive way. The world will hold Russia accountable.”
Biden said he would use a G7 meeting on Thursday morning to draw up “further consequences” for Russia’s action.
He said: “I will meet with my G7 counterparts in the morning and then speak to the American people to announce the further consequences the United States and our allies and partners will impose on Russia for this needless act of aggression against Ukraine and global peace and security.
“We will also coordinate with our Nato allies to ensure a strong, united response that deters any aggression against the alliance. Tonight, Jill and I are praying for the brave and proud people of Ukraine.”
What happens next?
Boris Johnson will chair a meeting of the government’s emergency Cobra committee in Downing Street at 7.30am to “discuss the response to the horrific attacks in Ukraine”, a spokesperson said.
The prime minister will later speak with other western leaders, including Joe Biden, to discuss a co-ordinated international response to the Russian invasion.
Johnson has been criticised for the sanctions the UK announced following Putin’s incursion into the Donetsk and Luhansk so-called “breakaway” regions of Ukraine.
However, the government has insisted that a “full-scale invasion” of Ukraine - as now seems to be happening - would lead to further economic and military reprisals.
In the House of Commons on Wednesday, Johnson confirmed that more British weapons were being sent to Ukraine.
At prime minister’s questions, he said: “In light of the increasingly threatening behaviour from Russia, and in line with our previous support, the UK will shortly be providing a further package of military support to Ukraine.
“This will include lethal aid in the form of defensive weapons and non-lethal aid.”