Seven Ukrainian troops have been killed in fighting in the volatile east overnight, officials said.
The Ukrainian army has been fighting pro-Russian rebels in the east for weeks, and hostilities have continued despite President Petro Poroshenko's promise this week of an upcoming ceasefire.
Vladislav Seleznev, spokesman for Ukrainian forces in the east, said seven soldiers were killed and 30 injured in fighting outside the village of Yampil. He said 300 rebels were killed, but that could not be immediately verified.
While Nato reported yesterday that Russia was resuming a military build-up at the Ukrainian border, Russian President Vladimir Putin has voiced concern about the Ukrainian military onslaught.
The UN says at least 356 people, including 257 civilians, have been killed in eastern Ukraine since May 7.