"Two Ukrainian soldiers were killed over the last day, three were injured," said spokesman Volodymyr Polyovy.
"One soldier was killed by a sniper's bullet, and one as a result of a shelling attack," he said.
The clashes are the latest violence to batter a fragile ceasefire deal between Kiev and the rebels, which has failed to stem fighting at flashpoints around the region.
Polyovy said insurgents "continued to violate the ceasefire agreement at several locations" over the past 24 hours, including at the airport in rebel hub Donetsk where Ukrainian positions were shelled twice.
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AFP correspondents in the separatist-controlled city, once the biggest in the region and home to about one million people, heard artillery strikes today morning.
Ukrainian President Petro Poroshenko yesterday held crunch talks with Russian President Vladimir Putin and key European leaders, without making any apparent progress on the crucial sticking points.
Poroshenko said after the talks that "the main problem is the implementation of the agreement" Kiev struck with the pro-Russian rebels on September 5, which commits both sides to stop firing.
The conflict in eastern Ukraine has killed over 3,400 people in the past six months, according to a "very conservative estimate" published in a UN report yesterday.