Ukraine crisis: 'Little doubt of Russian troop build-up on border'
19 June 2014 Last updated at 21:54 BST
Nato has urged Russia to "stop destabilising" the situation on the border with eastern Ukraine.
A limited truce has been observed in Luhansk, where rebels and government forces have been exchanging the bodies of their dead.
But the BBC's Daniel Sandford says there is now "little doubt" that there is a build up of Russian troops along the border.