US President Joe Biden has warned Russia will invade “in the coming days” as the UK embassy relocates from the Ukrainian capital.
In a speech in the White House, Mr Biden admitted he “is convinced” Russia will invade Ukraine.
While Mr Biden did not rule out diplomacy, he insisted the West remains prepared to strike back if Russia does invade, and target the capital of Kiev.
He added: “If Russia invades, they will have chosen war and the door to diplomacy will be closed shut.
“Russia has a choice between war and diplomacy.”
The Foreign, Commonwealth and Development Office (FCDO) announced that UK officials will “temporarily” relocate from the Ukraine capital to Lviv in the west of the country.
The move came after Moscow-backed separatists in eastern Ukraine announced an evacuation of their breakaway region’s residents to Russia.
The evacuation order came as a Western source stressed the crisis had entered its most dangerous phase.
With up to 190,000 Russian military personnel surrounding Ukraine, the source added that an attack could be launched at any time, with no notice and at significant scale, though an eleventh-hour diplomatic solution was still possible.
However, the evacuation order fuelled concerns that Russia may stage a “false flag” attack, possibly in the breakaway region, to justify an invasion after wrongly blaming such an atrocity on Ukrainian forces.
The Kremlin further rattled already frayed tensions with the West by announcing plans to stage massive drills of Russia’s nuclear forces on Saturday, overseen by President Vladimir Putin, and involving tests of cruise and ballistic missiles.
Announcing the evacuation on social media, Denis Pushilin, head of the self-proclaimed Donetsk People’s Republic, said Russia had agreed to provide accommodation for those who leave.
Women, children and the elderly should be evacuated first, according to the plan.
It came shortly before a report emerged from Russia’s RIA news agency of a large explosion in the centre of the separatist-held city of Donetsk in east Ukraine.
The other self-proclaimed region, Luhansk, made a similar evacuation announcement.
Millions of civilians are believed to live in the two rebel-held regions of eastern Ukraine; most are Russian speakers and many have already been granted Russian citizenship.
The eastern Ukraine conflict zone saw the most intense artillery bombardment for years on Friday, with the Kiev government and the separatists trading blame.
Amid the growing fears of war, Mr Putin ordered his emergencies minister to travel to the Rostov region which borders Ukraine, according to the IFAX news agency.
The Defence Ministry in Moscow has said some Russian military units are being withdrawn from areas near Ukraine.
But US Secretary of State Antony Blinken dismissed these claims, stressing at the Munich Security Conference that “on the contrary, we see additional forces going to the border including leading edge forces that would be part of any aggression,”
Shortly after the evacuation announcement in Donetsk on Friday, a Reuters witness said a loud warning siren sounded in the city centre.
People will start being bussed out of the Donetsk region at 8pm (5pm GMT) on Friday, Russia’s Interfax news agency cited a source saying.
Meanwhile, Michael Carpenter, US ambassador to the Organisation for Security and Cooperation in Europe, told a meeting of the monitoring group that the Russian troop build-up had grown significantly from the estimates of 100,000 Russian troops at the end of January.
“We assess that Russia probably has massed between 169,000-190,000 personnel in and near Ukraine as compared with about 100,000 on January 30,” he told the meeting, which Russia did not attend.
“This is the most significant military mobilisation in Europe since the Second World War.”
International monitors in the Donbas region of eastern Ukraine, the setting for a grinding eight-year conflict between Ukrainian military forces and Russian backed separatists, have reported a significant increase in hostilities over the past few days.
Reuters reported one diplomatic source considered the recent escalation to be the most intense fighting the region has seen since a 2015 ceasefire brought the first phase of the conflict to an end.
Monitors reported more than 500 explosions in the 24 hours to Thursday lunchtime - around four times the usual level of shelling in the area.
The West was on high alert on Friday for a possible Russian invasion of Ukraine amid the reports of fresh fighting between Ukrainian forces and Russian backed separatists in the east of the country.
Kiev and the rebels blamed each other for ceasefire violations as the US and Britain warned Russia was preparing a “false flag” operation to provide a pretext for launching an attack.
But even as the tensions continued to rise, the UK’s Security Minister Damian Hinds said there was “still a way out” if Russia chose the diplomatic route.
“We want to be working with Russia - one of the great nations of the world - we strongly encourage President Putin to step back and take that diplomatic route,” Mr Hinds told Sky News on Friday morning.
But he added: “There is no sign of it dissipating and that threat is there. It might be imminent it might take a little bit longer.
“We have to stand strong and we stand shoulder to shoulder with our friends in Ukraine.”
The Minister’s warning came as Western leaders prepared for another day of urgent diplomacy to try and find a solution to the crisis on Ukraine’s borders.
Prime Minister Boris Johnson will head to the Munich Security Conference this weekend and will reportedly take part in a meeting hosted by US President Joe Biden with the leaders of France, Germany, Italy, Poland, Romania, Canada, the EU and NATO on Friday, Politico reported.
The White House also confirmed last night that Mr Biden will speak with transatlantic leaders on a phone call about “Russia’s buildup of military troops on the border of Ukraine and our continued efforts to pursue deterrence and diplomacy”.
On Thursday, at a dramatic session of the United Nations Security Council in New York, Mr Blinken laid out how a Russian incursion could unfold in the coming days.
He said “missiles and bombs” could be dropped on Ukraine following a “manufactured provocation” for conflict, which could take the form of a “fabricated so-called terrorist bombing inside Russia”, or “a fake, even a real attack using chemical weapons”.
On Friday Russia’s Interfax news agency reported that the self-proclaimed Donetsk People’s Republic, which is backed by the Kremlin, said the village of Petrivske had been the target of shelling from the Ukrainian side.
Another self-proclaimed rebel republic, Luhansk, reported also several incidents of mortar fire on Friday morning.
Meanwhile Ukraine’s Joint Armed Forces posted on its Facebook site that after 60 ceasefire violations from the Russian backed separatists on Thursday there had so far been a further six on Friday.
But Moscow made further claims on Friday that it is continuing to pull troops back from the Ukrainian border. Interfax reported the Russian defence ministry was preparing for a convoy of tanks and armoured vehicles to return to base in its western military district after they took part in exercises
Foreign Secretary Liz Truss, who was visiting Kiev on Thursday, said reports alleging “abnormal military activity” by Ukraine in the eastern Donbas region were a “blatant” attempt by the Kremlin to fabricate a reason for an incursion.
Speaking at RAF Waddington in Lincolnshire, the Prime Minister added there was a “false flag operation designed to discredit the Ukrainians” and “we fear very much that that is a thing we will see more of over the next few days”.
He warned that Mr Putin would be “mad” to invade because it would result in a “bloody and protracted conflict”.
