The Russian president will personally monitor the exercise carried out by Russia's nuclear forces on Saturday, which will involve the launch of multiple ballistic and cruise missiles, Kremlin spokesman Dmitry Peskov said.

Mr Peskov said the exercises have been planned for a while and denied they signalled an escalation in the growing tensions between Moscow and the West as about 150,000 Russian troops gather at the border with Ukraine.

Moments after the announcement, US Defence Secretary Lloyd Austin said despite Russian claims it is moving troops back to their bases, more units are actually moving to the Ukraine border and there is no evidence they are moving away.

Mr Austin added: "It is ironic that what Mr Putin did not want to see happen was a stronger NATO on his flank - and that's exactly what he will see going forward".

Read more on the latest Ukraine news as Russia and the US defence ministers hold crunch talk

Still a diplomatic route

UK security minister Damian Hinds told Sky News on Friday the threat from Russia is still there despite Moscow claiming it is moving troops back to their bases after completing exercises.

He said: "There's still a way out, it's still with Russia, there's a diplomatic route and we strongly urge Russia to take that route but there is that build-up of troops on the border and there's no actual evidence of it dissipating, so that threat is there.

"It might be imminent or it might take a little bit longer, we're dealing with a regime here in President Putin who may pick his moment but we have to stand strong, we stand shoulder to shoulder with our friends in Ukraine."

The Ukraine military said there have been 600 ceasefire violations over the past 24 hours in Donbas, the Russian-backed separatist area of eastern Ukraine. One soldier was injured and there have been more than 300 explosions, the military said.

On Thursday, the shelling in the Donbas region led world leaders accused Russia of carrying out a "false flag" operation in which Moscow makes it seem like Ukraine is attacking them as a pretext for invading.

As the threat of an invasion has not lowered, according to Western leaders, Poland said it is ready to help people who would be forced to leave Ukraine if there was a Russian incursion, Polish Defence Minister Mariusz Blaszczak said during a joint news conference with his US counterpart in Warsaw.

Western leaders meeting this weekend

Boris Johnson and US President Joe Biden will hold a phone call about Ukraine this evening, UK time before the prime minister joins senior ministers at a security conference in Munich this weekend.

Late on Thursday, US Secretary of State Antony Blinken agreed to meet Russian Foreign Minister Sergei Lavrov late next week - provided Moscow doesn't invade Ukraine.

Efforts are continuing to prevent a conflict, amid fears that Russia is increasingly close to being able to mount an invasion.

Russia wants guarantees from the West, including the assurance that Ukraine will never join NATO, but the West is only willing to discuss arms control and confidence-building measures.

The Kremlin describes invasion fears as hysterical, but US President Joe Biden warned on Thursday that they could be preparing an excuse to move in.

Mr Biden said: "We have reason to believe they are engaged in a false flag operation to have an excuse to go in.

"Every indication we have is they are prepared to go into Ukraine and attack Ukraine."

Mr Blinken echoed these words, saying: "It could be a fabricated so-called terrorist bombing inside Russia, the invented discovery of a mass grave, a staged drone strike against civilians, or a fake - even a real - attack using chemical weapons.

"Russia may describe this event as ethnic cleansing, or a genocide."

Russia's deputy foreign minister Sergei Vershinin said Mr Blinken's comments were regrettable and dangerous.

The US president has said a number of times that Russia could invade Ukraine within days.

Mr Biden is expected to host a call later today with the leaders of Canada, France, Italy, Germany, Poland, Romania, the UK, the European Union, and NATO.

In other developments:

• UK Prime Minister Boris Johnson is expected at a security conference in Munich this weekend, along with Foreign Secretary Liz Truss and Defence Secretary Ben Wallace

• Belarusian President Alexander Lukashenko will meet Russian President Vladimir Putin on Friday to decide how much longer Russian troops will remain in his country for military drills

• The UK, Poland, and Ukraine agreed to "intensify" work to "strengthen democracy" in eastern Europe, including work on "defence and security, sanctions, energy security and countering disinformation"

• White House spokesperson Karine Jean-Pierre said that Russia had sent an extra 7,000 troops to the Ukrainian border over the past 24 hours, despite Russia's defence ministry saying some of its military units had left the area.