Russian forces have started military drills near Ukraine simulating the use of tactical nuclear weapons in response to what Moscow deems threats from western officials about increased involvement in the conflict.

Vladimir Putin ordered the drills earlier this month in a move Russian officials said was a warning to the west not to escalate tensions further.

The Kremlin has particularly been angered by the French president, Emmanuel Macron, who floated the possibility of sending European troops to fight Russia in Ukraine, and by remarks from the UK foreign secretary, David Cameron, who said Ukraine had the right to use weapons supplied by London to target sites in Russia.