The overall death toll reported for the past two days rose to 12 after the bloodiest outburst of violence since the former Soviet republic and its foes last month agreed an "indefinite" ceasefire.
The fighting came as Ukrainian President Petro Poroshenko urged German Chancellor Angela Merkel to step up economic sanctions against Moscow, and fears grew in Kiev that US support could wane should President Donald Trump draws closer to Russian leader Vladimir Putin.
"Since Sunday, there have been continuing clashes and heavy attacks on our positions," Ukraine's 72nd army brigade spokeswoman Olena Mokrynchuk told AFP.
An AFP reporter in the town of Avdiivka near the de facto rebel capital Donetsk saw Kiev troops capture three rebels today. Two of them later died of their wounds.
More From This Section
Electricity has been off since yesterday and water supplies are sporadic in Avdiivka amid the shelling and gunfire.
The separatists also reported two civilians deaths from Ukrainian fire around Donetsk.
The bloodshed put at risk yet another attempt by exasperated mediators to end one of Europe's bloodiest conflicts since the 1990s Balkans wars.
The violence coincided with Poroshenko's visit to Berlin to meet ally Merkel -- the German leader who along with French President Francois Hollande helped hammer out a 2015 peace deal in the Belarusian capital Minsk that has failed to achieve results.
"We believe that not only should the sanctions be maintained, but they should be intensified as well," he added.
Merkel said she found the situation "worrying" but gave no indication on whether she intended to add to the pressure on Putin.
Ukraine fears that staunch support from the United States could now dry up if Trump makes good on his campaign pledge to improve ties with Moscow.