Five Ukrainian servicemen were killed in fighting in eastern Ukraine on Wednesday, mostly near the government-held town of Maryinka where pro-Russian rebels were trying to make a significant advance, a presidential aide said.
Thirty-nine other Ukrainians were wounded, the aide, Yuri Biryukov, said on his Facebook page.
Ukraine's defence ministry said on Wednesday that the separatists, using tanks and artillery, had tried to take government positions near Maryinka, to the east of the rebel-held city of Donetsk, in violation of a ceasefire declared in February.
They were beaten back after nearly 12 hours of fighting, the defence ministry said.
The rebels blamed government troops for the fighting and said 15 civilians and separatist fighters had died in shelling by Kiev's forces.