The German and French foreign ministers made their first visit to Ukraine's war-torn east on Thursday, saying they wanted to push a new bid for peace after a recent surge in violence.

Frank-Walter Steinmeier and his French counterpart Jean-Marc Ayrault visited the Donetsk region and viewed a bridge destroyed in fighting between separatist and government forces in the city of Slavyansk.

Ayrault said the two men were looking "to create the conditions for a summit" between French President Francois Hollande, German Chancellor Angela Merkel, Ukrainian President Petro Poroshenko and Russian leader Vladimir Putin.

They were the architects of a peace deal drawn up in the Belarus capital Minsk in February 2015 which reduced the intensity of the fighting but has not succeeded in ending the conflict.

Ayrault said the ministers wanted to "create the conditions for a new way, a new step in the direction of peace."

The ministerial visit came after one of the bloodiest days in weeks on Tuesday which saw government forces and the separatists each lose three fighters.

"We need the fighting to stop so that advances can be made on the political front" Steinmeier said in comments published in the German Bild daily on Friday.

"We still have a lot of work to do to fully implement the Minsk accord," he added.

A United Nations report presented in Kiev on Thursday reported "escalation in hostilities and drastic increase in civilian casualties" in eastern Ukraine between May and August.

The UN High Commissioner for Human Rights Zeid Ra'ad Al Hussein said in the report that "the situation along the contact line remains deeply unstable" and "there is a real risk that a new outbreak of violence could happen at any time."

The report updated the conflict toll, saying that 9,640 people have been killed and 22,431 wounded on both sides.

- Protests over autonomy -

Ayrault and Steinmeier have urged Kiev's pro-Western leaders to commit more fully to the 13-point plan agreed in Minsk under which the rebels would get partial autonomy within a unified Ukraine, an initiative that is unpopular with many Ukrainians.

They faced protestors during a visit to Kramatorsk, another Kiev-controlled city in the conflict zone, where some 40 demonstrators protested against the plan to hand power to rebel-held Donetsk and Lugansk regions.

Protestors in front of the office of the OSCE, which monitors the conflict, held placards saying "We are Ukraine" and "No to a special status for Donbass," referring to eastern Ukraine's industrial heartland.

The German and French ministers met OSCE monitors who briefed them on ceasefire violations and showed them fragments of mines, grenades and other explosive devices found in the area.

In its latest report on Tuesday, the OSCE special monitoring mission recorded 275 explosions in the Donetsk region, compared with 57 the previous day.

It said many were concentrated in the towns of Avdiivka and Yasynuvata, just a few kilometres from the rebels' de facto capital of Donetsk.