Thirteen government soldiers and at least as many civilians have been killed in 24 hours in eastern Ukraine’s separatist conflict after the collapse of peace talks, a spokesman for the Kiev authorities said.

Hopes of easing the situation evaporated on Saturday with Ukraine’s representative and separatist envoys accusing the other of sabotaging negotiations.

“Fighting continues across all sections of the frontline,” Kiev’s military spokesman, Volodymyr Polyovy, said in a briefing.

The Organisation for Security and Cooperation in Europe (OSCE), which took part in the talks in Minsk, Belarus, along with envoys from Ukraine and Russia, said rebel delegates had not been ready to discuss key points of a peace plan.

“In fact, they were not even prepared to discuss implementation of a ceasefire and withdrawal of heavy weapons,” the OSCE said in a statement. It said rebels had instead pushed for a revision of a ceasefire plan agreed in Minsk last September.

The terms of that 12-point protocol have been repeatedly violated but Kiev and foreign governments see it as the only viable roadmap to end the nine-month conflict in which more than 5,000 people have been killed.

In eastern Ukraine, the Kiev military reported no let-up in rebel attacks on government positions. Clashes are intense around the town of Debaltseve, Polyyovy said, referring to a Kiev-held transport hub connecting the two main rebel strongholds that separatists aim to cut off. “There is no question of encirclement or cutting off of the main communication lines. The situation is under control,” he said.

The rebel advance has succeeded in seizing part of nearby Vuhlehirsk from Kiev troops, Polyovy said. On Sunday the town was being pounded by shelling, a witness reported.