"A powerful barrage began at 0450. There were many casualties. Krasnohorivka and Marinka are on fire," Deidei wrote.

"Close combat is taking place along the front line. The militants are going for a breakthrough," he said.

Earlier it was reported that 25 Ukrainian soldiers had been wounded during fighting for control of the town of Marinka, 10 kilometers west of the militant stronghold of the city of Donetsk.