Four Ukrainian servicemen died and another five were injured in the fighting at a roadblock near Kramatorsk, Donetsk region, Kyiv-based Information Resistance Group leader Dmytro Tymchuk said.

Members of illegal armed groups mounted "a massive assault" on the first roadblock near Kramatorsk last night, he wrote on Facebook on Friday morning, adding that the offensive was supported by eight Russian tanks and mortar fire.

"Law enforcers retaliating against the attack destroyed one tank of the terrorists and seized another tank. Four servicemen died and five were wounded. The militants blew up four armored personnel carriers and one mortar of ours," Tymchuk reported.

He also said the militants opened fire on Ukrainian army positions on Mount Karachun near Sloviansk. "A sniper wounded one serviceman," he said.

The militants stormed a military unit camp in Artemivsk early in the morning. The attack was suppressed without any army casualties, Tymchuk said.