COPENHAGEN (REUTERS) - Nato Secretary General Anders Fogh Rasmussen said on Friday a "Russian incursion" into Ukraine had occurred overnight, but stopped short of characterising it as an invasion.

"Last night we saw a Russian incursion, a crossing of the Ukrainian border," he told reporters after meeting the Danish defence minister. "It just confirms the fact that we see a continuous flow of weapons and fighters from Russia into eastern Ukraine and it is a clear demonstration of continued Russian involvement in the destabilisation of eastern Ukraine," the Danish Nato chief said.

Earlier, British reporters said they had seen Russian military vehicles crossing into Ukraine.