BORIS Johnson has warned Vladimir Putin it would be a “disastrous step” to invade Ukraine.

The Prime Minister said it would be “painful, violent and bloody business” for Russia if its troops crossed the border into its democratic neighbour.

Visiting a hospital in Milton Keynes as the Foreign Office pulled some embassy staff out of Kyiv, Mr Johnson said: “We do think it prudent to make some changes now.

“The intelligence is very clear that there are 60 Russian battle groups on the borders of Ukraine, the plan for a lightning war that could take out Kyiv is one that everybody can see.

“We need to make it very clear to the Kremlin, to Russia, that that would be a disastrous step.”

With more than 100,000 Russian troops massed along the Ukrainian border and MI6 warning President Putin wants to install a pro-Russian puppet regime, Mr Johnson said intelligence around the situation was “pretty gloomy” but war was not inevitable.

The Prime Minister also said the UK was “leading on creating a package of economic sanctions” against Russia and he would be speaking to international allies later today.

He said: “We also need to get a message that invading Ukraine, from a Russian perspective, is going to be a painful, violent and bloody business. I think it’s very important that people in Russia understand that this could be a new Chechnya.”

Russia's attempts to suppress independence in Chechnya in the 1990s and 2000s saw thousands killed in a brutal guerilla war.

Mr Johnson said he had visited Ukraine and knew the people of the country, adding: “My judgment is that they will fight.”

Asked if he believed an invasion was imminent, he said: “I’ve got to tell you that I think the intelligence is pretty gloomy at this point. There is certainly a very, very large array of Russian forces and we have to take the necessary steps.

“I don’t think it’s by any means inevitable now, I think that sense can still prevail.”

Meanwhile Ireland’s foreign affairs minister has said that plans by Russia to hold military exercises off the coast of Ireland are “not welcome”.

Simon Coveney said the exercises were due 240 kilometres (150 miles) off the south-west Irish coast in international waters but within Ireland’s exclusive economic zone.

Ahead of a meeting of EU foreign ministers, Mr Coveney said: “We don’t have a power to prevent this from happening. But I have made it clear to the Russian ambassador in Ireland that it’s not welcome. This is not a time to increase military activity and tension in the context of what is happening with and in Ukraine at the moment.”

He added: “This is an important day today for EU foreign ministers to reinforce a message of unity from the European Union in relation to Russian/Ukraine tension.

“There are two very clear messages that EU foreign ministers will want to get across today.

“First of all, a clear message and ask of Russia to defuse tension in the context of their activities on the border of Ukraine, and give reassurance to the rest of the world in terms of their intentions.”