According to Reuters report, Iranian state TV said that shortly after midnight "three drones were observed in the sky over Isfahan. The air defence system became active and destroyed these drones in the sky."

Israel reportedly attacked Iran on late Thursday, reported Reuters on Friday, citing people familiar with the matter. This incident follows days after Iran initiated a retaliatory drone strike on Israel.

However, one of the sources told Reuters the U.S. was not involved but was notified by Israel before the attack.

Senior Iranian official told Reuters after reported strike that there is no plan for immediate retaliation. The official also said that no clarification on who is behind incident.

Iran's Fars news agency reported three explosions were heard near an army base in the central city of Isfahan. An Iranian official told Reuters there was no missile attack and the explosions were the result of the activation of Iran's air defence systems.

According to Reuters, Iran's senior commander Mihandoust said, "noise heard in Isfahan overnight was caused by air defence targeting one suspicious object."

The broadcaster later said the situation in Isfahan was normal and no ground explosions had occurred. Meanwhile, the International Atomic Energy Agency (IAEA) claimed that Iran's nuclear sites have remained damage free, as per Reuters.

An Iran analyst told state TV that the it was attacked by infiltrators within country via mini drones, reported Reuters.

Several Iranian nuclear sites are located in Isfahan province, including Natanz, centrepiece of Iran's uranium enrichment program.

Iran Fires Air Defence Batteries

Iran fired air defence batteries early Friday morning after reports of explosions near a major airbase at the city of Isfahan, reported AP, citing the state-run IRNA news agency.

It remained unclear if the country was under attack. However, tensions remain high after Iran’s unprecedented missile-and-drone attack on Israel. One government official suggested sites may have been targeted by drones.

IRNA said the defences fired across several provinces. It did not elaborate on what caused the batteries to fire, though people across the area reported hearing the sounds.

In particular, IRNA said air defences fired at a major airbase in Isfahan, which long has been home to Iran's fleet of American-made F-14 Tomcats — purchased before the 1979 Islamic Revolution, reported AP.

(With Inputs From Agencies)