Ukraine’s capital Kyiv came under a large-scale Russian drone and missile attack overnight into Saturday, just hours after Russia and Ukraine began a major prisoner exchange.

Ukraine’s capital came under a large-scale Russian drone and missile attack overnight and into early Saturday that left at least 15 people injured, according to Ukrainian officials. Explosions and machine gun fire were heard throughout Kyiv as many sought shelter in subway stations.

Reuters witnesses saw and heard successive waves of drones flying over Kyiv, and a series of explosions jolted the city.