The Ukrainian president has used a summit of EU leaders to call for tough action against Russia over the separatist conflict in Ukraine's eastern regions.
Petro Poroshenko called on the EU "to demonstrate a strong position of action by the European Union to support Ukraine" during their meeting in Brussels on Wednesday, a statement posted on his website said.
The president said he had spoken to Herman Van Rompuy, the president of the European Council, after intense fighting in the east, in which Kiev has alleged Russian involvement in an air raid on a residential area and the shooting down of a military transport plane.
Poroshenko told Van Rompuy there was new evidence of rebel fighters crossing into Ukraine from Russia.
The latest round of diplomatic manoeuvering comes as mediators on the Ukraine crisis accused pro-Russian rebels of not being committed to truce negotiations.
A discussion meant to be held Tuesday between the trilateral Contact Group - which includes representatives of Ukraine, Russia and the OSCE - and separatist leaders "did not materialise" despite several attempts to convene it, sources said.
Meanwhile, diplomats in Brussels said EU leaders were likely to give the go-ahead on Wednesday to new sanctions, though they may fall short of the far-reaching economic measures sought by the US and some of the hawkish members of the EU, including Poland and the Baltic states.
Ukraine has accused Russia repeatedly of turning a blind eye to Russian fighters crossing the long shared border to team up with rebels, often with Russian weapons and military equipment. Moscow has repeatedly denied the allegations.