A loud blast heard near the Iranian city of Isfahan was caused by "air defense firing at a suspicious object," an Iranian senior military commander said, according to Iran's state-aligned Tasnim news agency.
There was no "damage or incident," said senior military commander Second Brigadier General Mihandoust in Isfahan province, according to Tasnim.
A US official told CNN that Israel had carried out a strike inside Iran. The Israeli military has not commented.
Iranian state media are reporting that all facilities in the area are secure, including significant nuclear facilities.
Three explosions were heard early Friday near the military base where fighter jets are located in Isfahan province, Iran's semi-official FARS news agency reported.
"The defense is activated in response to an object that is likely to be a drone," sources tell FARS news.
Iran's National Cyberspace Center spokesman, Hossein Dalirian, said air defenses shot down three drones and "there are no reports of a missile attack for now."