The US has warned Russia that its actions in Ukraine are “extremely dangerous and provocative”.

The White House says it has been unable to verify claims by Ukraine President Petro Poroshenko that government forces have destroyed part of a Russian military convoy it says crossed over its border. Poroshenko told British Prime Minister David Cameron over the phone that his forces had destroyed the convoy.

American officials warned Russia it has no right to send vehicles into Ukraine without permission. The White House said last night:

"The escalation in Russian activity designed to destabilise Ukraine in recent weeks is extremely dangerous and provocative."

Russia has denied any of its troops were in Ukraine and has reassured the Pentagon that there are no military personnel in the aid convoys. If Ukraine’s claims are true it would mark a significant escalation in the tense situation and the first direct military conflict between the two nations since the crisis began.