Iran's state media reported explosions in the central province of Isfahan on Friday, as US media quoted officials saying Israel had carried out retaliatory strikes on its arch-rival.

Iranian media said no major damage was reported.

"Reports indicate there was no major damage or large explosions caused by the impact of any air threat," the official IRNA news agency said.

Air defence systems over several Iranian cities had been activated.

Israel had previously warned it would hit back after Iran fired hundreds of missiles and drones at Israel over the weekend. Most of them were intercepted. It followed an April 1 strike on the Iranian consulate in Damascus that was widely blamed on Israel.

Iran's Fars news agency reported "three explosions" were heard near the Shekari army airbase in the northwest of Isfahan province, while Iran's space agency spokesman Hossein Dalirian said "several" drones had been "successfully shot down".

"There are no reports of a missile attack for now," Dalirian said on social media platform X.

Nuclear facilities in Isfahan were reported to be "completely secure", Iran's Tasnim news agency reported, citing "reliable sources".

ABC and CBS News reported the strikes had been carried out by Israel, quoting US officials. There was no immediate comment from the White House or Pentagon.

CNN quoted an official as saying the target of the Israeli attack was not nuclear.

The Israeli military told AFP: "We don't have a comment at this time."

Israeli Prime Minister Benjamin Netanyahu, who has vowed to destroy Hamas over its October 7 attack that started the Gaza war, has stressed that Israel "reserves the right to protect itself" against Iran.

The United States, Israel's main ally and military supplier, has made clear it would not join a reprisal attack on Iran, but unveiled sanctions against people and entities involved in producing the drones deployed in the Iranian assault.

"We are holding Iran accountable," US President Joe Biden said on Thursday, announcing the measures after the European Union said it would also sanction Iran's drone programme.

Iranian Foreign Minister Hossein Amir-Abdollahian had warned that Tehran would make Israel "regret" any attack on the Islamic republic.

Flights were suspended across swathes of Iran on Friday.

"Iran's air defence has been activated in the skies of several provinces of the country," Tehran's official IRNA news agency said.

Mehr news agency reported that "flights to Tehran, Isfahan and Shiraz, and airports in the west, northwest and southwest have been suspended."

Flight-tracking software showed commercial flights avoiding western Iran, including Isfahan, and skirting Tehran to the north and east.

On Thursday, UN Secretary-General Antonio Guterres painted a dark picture of the situation in the Middle East, warning that spiralling tensions over the war in Gaza and Iran's attack on Israel could devolve into a "full-scale regional conflict."

"The Middle East is on a precipice. Recent days have seen a perilous escalation – in words and deeds," Guterres told the Security Council.

"One miscalculation, one miscommunication, one mistake, could lead to the unthinkable – a full-scale regional conflict that would be devastating for all involved," he said, calling on all parties to exercise "maximum restraint." (AFP)