Ukrainian army fire has killed one person and wounded another in the pro-Moscow rebel bastion of Donetsk, despite a truce that had held for several weeks, separatists have said.

The rebels' self-styled "defence ministry" said both casualties from Saturday's incident were civilians, although an earlier report cited by Russian news agency Interfax said it was actually a rebel fighter who died.

It was unclear what weapons had been fired, with the rebels first claiming Ukrainian forces had used tank fire, and then saying there were mortar rounds.

The Ukrainian army condemned what it described as a "provocation aimed at destabilising the situation in the east," spokesman Vladislav Seleznev told the AFP news agency.

"Under no circumstance would we ever fire against civilians," he said.

The Organisation for Security and Cooperation in Europe (OSCE), whose observers are deployed in eastern Ukraine, could not immediately comment on the incident.

Ukraine has been fighting pro-Russia rebels since early 2014 when mass protests brought down a pro-Russian government and replaced it with one seeking closer ties with the EU and US.

Kiev accuses Moscow of direct military involvement in the conflict, as well as military support for the separatists, a charge Russian officials deny.

More than 8,000 people have been killed in the conflict so far, according to the UN.

Al Jazeera