President Volodymyr Zelenskiy announced he would convene a Ukrainian security council meeting to discuss the fighting, calling it a “cynical provocation” and an attempt to disrupt the peace process.

A simmering conflict between Ukrainian troops and Russian-backed forces in eastern Ukraine has killed more than 13,000 people since 2014 despite a ceasefire agreement struck in 2015.

Ukraine, Western countries and NATO accuse Russia of sending troops and heavy weapons to prop up separatist fighters in the Donetsk and Luhansk regions, a charge that Moscow has denied.

The fighting came as Ukraine and Russia are gearing up for another summit, alongside the leaders of France and Germany, to try to end the fighting.

“This is not just a cynical provocation … it is an attempt to disrupt the peace process in the Donbass, which had begun to move though small but continuous steps,” Zelenskiy said in a statement.

Zelenskiy came to power last year promising to end the conflict. Ukraine and Russia have implemented some confidence-building measures, including prisoner swaps and phased troop withdrawals in designated areas.

Zelenskiy and Russian President Vladimir Putin spoke by phone last week, Zelenskiy’s office said. (Reporting by Natalia Zinets; Writing by Matthias Williams; Editing by Alex Richardson)