Four Ukrainian servicemen were killed and five wounded in an overnight attack by separatist fighters on a military post in the east of the country, a military analyst said on Friday.

Dmytro Tymchuk, who has good sources among government forces, said the rebels, backed by eight Russian tanks and firing mortar bombs, stormed a military base near Kramatorsk in one of several rebel attacks overnight.

"In return fire by government forces, one terrorist tank was destroyed and one tank captured," Tymchuk said on his Facebook page. "Four service personnel were killed, five wounded," he added.

He had no estimate of casualties on the rebel side. There was no immediate comment from the separatist fighters.

The attacks took place despite a week-long government ceasefire which is due to end at 10 p.m. and which Kiev says has been breached numerous times by the rebels over the past week.

In other fighting, Tymchuk said, rebels again attacked forces taking part in the government's "anti-terrorist operation" on a hill near the city of Slaviansk and one Ukrainian soldier was wounded by sniper fire.

Rebels also attacked a military base in the early hours at Artemivsk, using tank and other fire. Ukrainian forces repelled this attack without any casualties, he said.