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.

Russian forces have launched more than 500 aerial weapons at Ukraine overnight, Kyiv said on June 29, describing the attack as the biggest air strike on the country since the war began.

The U.N. Human Rights Monitoring Mission in Ukraine said in a report published Thursday that short-range drone attacks killed at least 395 civilians and injured 2,635 between the start of the war and last April. Almost 90% of the attacks were by the Russian armed forces, it reported.