At least 13 Ukrainian soldiers have been killed in a rebel attack at a Ukrainian military check point in the eastern Donetsk region early Thursday, the country's acting President Alexandr Turchynov said.
"Our troops defended the town of Volnovakha and have not allowed insurgents to break through defences, but unfortunately, our soldiers sacrificed their lives for Ukraine, tolerating mortar fire and heavy weapon fire," Xinhua quoted Turchynov as saying during his meeting with local religious figures.
Earlier in the day, the country's defence ministry said heavy casualties were expected after insurgents attacked the check point with rocket-propelled grenades and mortars, causing a Ukrainian armoured vehicle to ignite and triggering a massive explosion.
There has been no official word on rebel casualties, but local media cited sources in the separatist camp as saying 25 insurgents were injured.
The incident comes just three days before the presidential elections in Ukraine scheduled for May 25, triggering fears of possible disruption of the vote in the eastern part of the country.
According to the Central Election Committee, as of Thursday afternoon, 18 of 34 regional election commissions in Lugansk and Donetsk regions were blocked by separatists, who seek independence from the central government in Kiev.