Ukrainian authorities said four soldiers had been killed in fighting Russia-backed separatists, some of the worst violence in weeks in war-torn eastern Ukraine.
Kyiv military spokesman Oleksandr Motuzyanyk and Defense Minister Stepan Poltorak said the clashes occurred January 29 near Avdiyivka, a town north of the regional center Donetsk.
The town is home to a major coke producing plant and a steel smelter.
Motuzyanyk said at least one separatist fighter was killed in the fighting which involved large-caliber mortars and artillery.
Fighting in eastern Ukraine, which erupted nearly three years ago, has ebbed and flowed amid repeated efforts to cement a lasting cease-fire.
The latest truce was announced in December.
More than 9,750 people have died in the conflict, which began shortly after Ukrainian President Viktor Yanukovych fled amid violent antigovernment protests in Kyiv in February 2014.