It was hard to return fire during the Svitlodarsk arc engagement in Donbas because militants attacked Ukrainian Anti-Terrorist operation (ATO) positions from the territory of Debaltseve, Vuhlehirsk and Kalynivka, battalion commander Major General Oleksandr Syrsky said.

"Notably, the enemy's artillery was firing from within the populated localities of Kalynivka, Vuhlehirsk and Debaltseve and that made impossible an adequate response because civilian casualties needed to be avoided," he told a press briefing in Kyiv on Monday.

A total of 34 122mm shells and 694 120mm and 82mm mortar mines were fired on Ukrainian army positions in the past 24 hours, he said.

In the opinion of Syrsky, the militants seek to advance towards Luhanske in the Donetsk region and to take over strategic sites.

All is quiet on the Svitlodarsk arc at the moment, he said.

The latest reports have said that six Ukrainian servicemen were killed in the clash.

The self-proclaimed Luhansk People's Republic (LPR) militants said earlier they had deterred the Ukrainian army's attempt at breaking through defense lines near the village of Kalynivka.

Kyiv said, in turn, that the Ukrainian army deterred the militants' attempt at driving forward units away from their positions in a two-hour engagement on Sunday, December 18.