Russia and Ukraine exchanged hundreds more prisoners Saturday as part of a major swap that amounted to a rare moment of cooperation in otherwise failed efforts to reach a ceasefire.

Russia launched a major attack on the Ukrainian capital Kyiv and killed at least 13 people in strikes across the country as the two sides released hundreds more prisoners on the second day of a major prisoner exchange.

Russian strikes killed at least 12 people in Ukraine overnight into Sunday, officials said, as Kyiv and Moscow traded fire amid an ongoing major prisoner swap. Ukraine’s emergency services described a night of “terror” as Russia launched a second straight night of major airstrikes on Ukraine,