Amid fierce fighting in eastern Ukraine, government forces claim they are tightening the noose on pro-Russian separatists.
They say the latest clashes erupted after rebels refused to lay down their arms under a peace plan proposed by new President Petro Poroshenko.
Both Ukrainian government and rebel accounts of the fighting near Krasny Liman, north of the main regional hub of Donetsk, suggested a major battle involving armoured vehicles including tanks.
NATO’s Secretary-General meanwhile, on a visit to London, has raised fresh alarm about Russia’s possible intentions, claiming at least a few thousand more of its troops are now on Ukraine’s long, eastern border.
“We are now seeing a new military build up, a Russian military build-up along the Ukrainian border and it is indeed a matter of grave concern,” said Anders Fogh Rasmussen, standing alongside British Prime Minister David Cameron.
“We call on Russia to stop destabilising the situation in eastern Ukraine and engage in a constructive manner with the political leadership in Kyiv.”
As one key rebel leader acknowledged his pro-Russian separatists were outgunned, President Poroshenko said he would sign a controversial association agreement with the EU on June 27, shifting Ukraine further away from Moscow’s influence.