"We are seeing Ukrainian troops' attempts to carry out sabotage and strike Russian territory," the Russian defence ministry said in a statement. "If such cases continue, the Russian armed forces will strike decision-making centres, including in Kyiv."

Since President Vladimir Putin sent troops to Ukraine on February 24, Moscow has accused Kyiv forces of attacking territory in southern Russian.

Earlier this month Russian troops pulled back from areas north of Kyiv and are now refocusing their efforts on capturing more territory in eastern Ukraine.

The Russian defence ministry confirmed that its troops had now full control of the port in the besieged city of Mariupol.

The ministry added that Ukrainian troops and members of the Azov battalion had been encircled and "deprived of the opportunity to escape".

Members of the Azov battalion have been fiercely fighting Russians in Mariupol, located in the country's southeast between Russia-occupied Crimea and pro-Russian separatist regions in Ukraine's east.