At least 21 people were killed and 37 others were wounded in clashes between government troops and insurgents in eastern Ukraine over Sunday, authorities said Monday.
It was one of the bloodiest days since a ceasefire inked by the two sides early this month faltered, Xinhua reported.
Three civilians were killed and five others wounded in Donetsk city when artillery fire hit several buildings in the residential area, the city council said.
In a separate incident, seven government troopers were killed and nine others wounded when insurgents ambushed their armoured vehicle near Donetsk airport, said Yuri Biryukov, Ukraine's presidential advisor.
Rebel forces said that in another incident, 11 insurgents were killed and 23 others wounded in a crossfire at Donetsk airport.
Fierce confrontation between the two warring sides have left over 3,000 people dead and some 8,000 others wounded since mid-April.