Russia has battered Ukraine overnight with its largest drone attack since the war began, Ukraine’s military said Sunday, as Moscow intensified its military assault despite holding direct peace talks with Kyiv Friday.

Russia and Ukraine agreed to exchange 1,000 prisoners of war each during peace talks held in Istanbul on Friday, in what would be the biggest prisoner swap of the conflict. The negotiations, which lasted less than two hours and were mediated by Turkey, marked the first time the nations have engaged in direct peace talks since the war began.

Many Russian soldiers say they would see a cease-fire along the current front lines as a failure, hinting at the nationalist discontent the Kremlin could face in accepting a cease-fire.