Pro-Russian insurgents have killed seven Ukrainian servicemen and wounded eight others in an ambush near the eastern city of Kramatorsk.
The Ukrainian Defence Ministry said in a statement that the Ukrainian BTR convoy was attacked by more than 30 militants using grenade launchers and small arms while it was passing a bridge near Oktyabrske village, which is about 20km from Kramatorsk.
"After the first salvo, opened by the terrorists with heavy weapons, two Ukrainian soldiers died and three more were wounded," the statement said.
The ambush killed six soldiers, while the seventh died on the way to the hospital, according to the Ukrainian State Security Service (SBU).
The attack, which also claimed the life of one rebel fighter, represents the Ukrainian Army's greatest loss of life in a single incident since the government launched the 'anti-terrorist operation' to restore control in the largely Russian-speaking east, last month.
Ukraine Defence Minister Mykhailo Koval said that before the Kramatorsk incident, a total of nine Ukrainian soldiers had been killed, including five pilots.
Kramatorsk is in the northern part of the Donetsk region, which along with Luhansk held referendums for independence from Ukraine on 11 May.
Around 89% and 96% had voted in favour of 'self-rule' in Donetsk and Luhansk respectively, but those results were called 'illegal' by Ukraine and the West, BBC News reported.
Moreover, the separatists in Donetsk have appealed to Moscow for its accession into the Russian Federation.
In response, Russia has called for talks between Ukraine's central and south-east regional government, instead of endorsing the separatists' bid for annexation.