PROSPECTS for peace in eastern Ukraine are bleak, underscoring the need to uphold a shaky ceasefire between government forces and pro-Russian separatist rebels, a senior official from the OSCE security watchdog has warned.

Swiss diplomat Heidi Tagliavini, the Organisation for Security and Cooperation in Europe's envoy to the Trilateral Contact Group that includes senior representatives from Ukraine and Russia, said there was no alternative to peace accords signed in Minsk in September, no matter how dire the situation.

She told a meeting of the 57-member OSCE in Vienna: "Whatever their shortcomings may be and wherever they may need to be supplemented, the (Minsk) documents are the door on the road to peace in eastern Ukraine and will continue to be so."

The fighting in eastern Ukraine has killed an average of 13 people each day in the eight weeks since the ceasefire agreement, UN High Commissioner for Human Rights, Zeid Ra'ad Al Hussein, said.

At least 4,317 people have been killed and another 9,921 wounded since April.

The OSCE's special monitoring mission (SMM) in eastern Ukraine said military personnel shot at one of its convoys near the rebel stronghold of Donetsk on Wednesday. It did not say which side was responsible for the firing, the first time it has been targeted.