KYIV, Ukraine (AP) — Russia launched its biggest aerial attack against Ukraine overnight, a Ukrainian official said Sunday, part of an escalating bombing campaign that has further dashed hopes for a breakthrough in efforts to end the 3-year-old war.

Russia launched 537 drones and missiles into Ukraine overnight into Sunday morning, according to Ukraine's air force.

Moscow has been escalating its bombardment of Ukraine over the past several months as U.S.-mediated peace talks stall.