According to reports received, the soldiers were killed when a separatist shell hit their armored personnel carrier.
"Seven (Ukrainians) were killed late last night not far from Donetsk airport," spokesman Andriy Lysenko is quoted as saying by Reuters.
It was the largest loss of life among Ukrainian soldiers in a single incident since the ceasefire began on Sept. 5.
It has also been learnt that nine more Ukrainian soldiers were wounded in the attack and that separatist tanks had been destroyed in return fire.
On the other hand, in another rebel attack, three civilians were killed and five injured in eastern Ukraine's rebel-controlled city of Donetsk, media reported on Monday.
Ukraine President Poroshenko called the cease-fire, under pressure from Western governments, after his troops suffered big battlefield losses against the separatists in August.
Ukraine has accused Russia of supporting the rebels by providing arms and ammunition. But, Moscow denied all the charges.
A recent data released by United Nations showed that more than 3,500 people had been killed in the ongoing conflict, including 298 people who died when a Malaysian passenger plane flying over eastern Ukraine was brought down in July.
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