At least 19 soldiers and civilians were killed in clashes across eastern Ukraine as fierce fighting raged between government forces and pro-Russian rebels following the collapse of ceasefire talks.

Ukraine's military said on Sunday that 13 soldiers had died and 20 were wounded over the past 24 hours, pushing the military death toll over the past two days to 28, according to the AFP news agency.

Unfortunately the peace process is now under threat Valeriy Chaly, Ukraine presidential aide

Six civilians also died in fighting across the rebels' self-declared Donetsk People's Republic and in Kiev-controlled towns in Luhansk region, government officials and separatists said.

The latest casualty reports came as Ukraine's two warring sides looked further than ever from agreeing a peace deal after the collapse of truce talks on Saturday at the Belarusian capital Minsk.

Al Jazeera's Charles Stratford, reporting from Yenakievo, said he heard a "barrage of shelling" that forced people to take cover on Sunday afternoon.

"The streets are virtually deserted and those people that can are hiding in their basements," he said, adding that many people have been trapped in their "cold and damp" houses in the middle of winter, without running water or electricity.

Yevdokiya Bugay, an 86-year old pensioner from Yenakievo, was pulled out from her destroyed house.

"I'm trembling. I live alone. I was sitting in the corner and I only just survived," she told Al Jazeera.

Mediators and Ukrainian representatives accused the separatists of refusing an agreement despite growing international pressure to defuse a bloody upsurge in fighting that has left scores dead in recent days.

The Organization for Security and Co-operation in Europe (OSCE), which is involved in the talks along with Russia, said that rebel negotiators in Minsk "were not even prepared to discuss implementation of a ceasefire and withdrawal of heavy weapons."

Instead the rebel representatives called for a total revision of an earlier Kremlin-backed peace plan signed in September that has formed the basis for all negotiations, the OSCE said in a statement.

Redrawing demarcation lines

The rebels said they now want to redraw the demarcation line between the two sides to include gains they have made since ripping up a shaky truce and pushing into Ukrainian territory.

Kiev has rebuffed this demand and said the rebels' position has thrown any future peace talks into doubt.

"Unfortunately the peace process is now under threat," Valeriy Chaly, the deputy head of Ukraine's presidential administration wrote on his Facebook page.

The fiercest fighting on the ground is focused around the strategic town of Debaltseve, a railway hub between rebel bastions Donetsk and Luhansk, where rebels are trying to encircle government forces.

Ukraine military spokesman Volodymyr Polyovyi said that "constant battles" were ongoing around the town but denied rebel claims that they have trapped some 8,000 government troops.

Civilians who have fled describe increasingly dire conditions in the town - which once had a population of some 25,000 - with water and electricity cut and the remaining inhabitants living in underground shelters.

Western governments and Ukraine have accused Russia of sending regular troops and arms to bolster the rebels and spearhead the latest offensive - claims Moscow has repeatedly denied.