Ukraine has key demands from Russia as well. Kyiv refuses to cede more territory to Moscow, including those in partially occupied regions. Also, Ukraine is seeking the return of children illegally deported to Russia and thousands of civilians detained in Russian prisons.

The barrage comes less than 24 hours after Russian President Vladimir Putin discussed details of the U.S. proposal for a 30-day ceasefire with a U.S. envoy.

Russia and Ukraine continued aerial attacks on each other, inflicting injuries and damages, officials said early on Sunday, as the fate of a proposed ceasefire to the three-year-old war remained uncertain.