In Ukraine, police in riot gear surround the local government headquarters in the eastern city of Kharkiv.

Pro-Russian protesters occupying the building were cleared during what was described by the interior minister as an “anti-terrorist operation.”

Seventy people were detained.

Angry demonstrators gathered outside demanding a referendum about their region joining Russia.

Vladen Kharkiv, a local resident explained: “The situation in Kharkiv is being escalated solely by the Russian side. It is in Russia’s interest to take back Kharkiv, Donetsk and Luhansk under Russian control. It’s in its interest.”

NATO warned Moscow of “grave consequences” to its relationship with the West if it intervened further in Ukraine.

John Kerry, US Secretary of State, said:

“Russia’s clear and unmistakable involvement in destabilising and engaging in separatist activities in eastern Ukraine is more than deeply disturbing.

“No one should be fooled and believe me, no one is fooled, by what could potentially be a contrived context for military intervention just as we saw in Crimea,” he added.

Russian Foreign Minister Sergei Lavrov dismissed US accusations that Moscow was destabilising Ukraine.

“Regarding the question about who was provoking and who is provoking the events in Ukraine, our American partners are probably trying to treat the situation based on their usual behaviour,” said Lavrov.

Meanwhile Ukrainian military personnel carriers were seen on a motorway outside the eastern Ukrainian city of Luhansk.

They were heading towards the city’s airport.

Pro-Russian separatists have taken over the regional headquarters of the security services in Luhansk.