TEHRAN — Iran’s defense minister confirmed Friday that Iranian warplanes had fired at a US drone last week but said they had taken the action after the unmanned aircraft had entered Iranian airspace.

The assertions by the defense minister, Brigadier General Ahmad Vahidi, were the first acknowledgment from Iran that the episode had happened. He spoke less than 24 hours after the Pentagon first disclosed the shooting, involving two Iranian jet fighters and the US aircraft, a Predator surveillance drone, during what US officials described as a routine surveillance mission Nov. 1 in international airspace over the Persian Gulf.