Russian President Vladimir Putin will respond to the Ukrainian drone strikes that destroyed Russian military aircraft in several locations on Sunday, President Donald Trump said on Wednesday.

President Trump spoke with President Vladimir V. Putin of Russia amid escalating attacks between Russia and Ukraine, even as their officials have been engaged in direct talks.

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.

Delegations from the warring sides met for barely an hour and agreed to exchange more prisoners of war - focusing on the youngest and most severely wounded - and return the bodies of 12,000 dead soldiers.