Ukraine’s security service released footage Wednesday of its attack on Russian war planes at multiple airbases across the country. In the span of a few hours on Sunday, nearly a third of Moscow’s strategic bomber fleet was destroyed or damaged with cheaply made drones sneaked into Russian territory, according to Ukrainian officials.

The barrage, one of the fiercest of the three-year war, struck six Ukrainian territories, killing at least six people and injuring about 80, Ukrainian officials said.