Iran's state media reported explosions in the central province of Isfahan Friday, as US media quoted officials saying Israel had carried out retaliatory strikes on its arch-rival.
Air defence systems over several Iranian cities were activated, state media reported, after the country's official broadcaster said explosions were heard near the city of Isfahan.
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.
Iran's Fars news agency reported "three explosions" were heard near Qahjavarestan, near Isfahan airport and the Shekari army airbase, while Iran's space agency spokesman Hossein Dalirian said "several" drones had been "successfully shot down".
Dalirian said on social media platform X there were "no reports of a missile attack".
"Reports indicate there was no major damage or large explosions caused by the impact of any air threat," the official IRNA news agency said.
Nuclear facilities in Isfahan were reported to be "completely secure", Iran's Tasnim news agency said.
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."
Blasts were also reported in southern Syria, according to a local activist group.
"There were strikes on a Syrian army radar position," said Rayan Maarouf, who runs the Suwayda24 anti-government website that covers news from Sweida province in the south.
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."
Oil prices surged more than three percent in early Asian trade on Friday following the reports of explosions.
