State media also said Iran fired its air defence systems after reports of blasts near the city of Isfahan, which forced the country to impose flight restrictions.

Tasnim, a state news agency, reports air traffic has since been cleared to resume at some airports.

Middle East latest - follow live updates after reports of explosions

Iran's state-run IRNA news agency said its air defences fired across several provinces, while the country's senior commander Siavosh Mihandoust said no damage has been caused.

He claimed an explosion came from air defence systems targeting "one suspicious object".

Iranian state TV said three drones were "destroyed" over Isfahan shortly after midnight, but later said the situation in the city is normal and no ground explosions had occurred.

Sky News' US partner NBC News reports Israel carried out an operation in Iran, citing a person familiar with the matter, with officials notifying US officials a response was coming.

Israel's military has not commented, but had promised a response to Iran's attack over the weekend.

A major airbase for the Iranian military is in Isfahan, where there were reports of blasts, as well as sites associated with its nuclear program.

Iranian state TV said its nuclear facilities remain unharmed, Reuters news agency reported.

Sky News' military analyst Michael Clarke said Isfahan "would make sense" as a target as it's home to one of the least sensitive nuclear sites.

"It's a research site, about 3,000 or so scientists work there and there's no evidence this was targeted on the nuclear site," he added.

"But the fact that Isfahan is one of the cities that does quite a lot of nuclear work is also symbolically quite important, I think, if the Israelis are indicating that they're not frightened to go after these sites."

It's over 1,000 miles to Isfahan from Israel, which suggests this was not a drone attack, Mr Clarke said, adding it was "almost certainly" led by Jericho missiles.

Dubai-based carriers Emirates and FlyDubai began diverting around western Iran at about 4.30am local time.

They did not explain, though local warnings suggested the airspace may have been closed.

Tensions remain high in the Middle East after Iran's missile and drone attack on Israel over the weekend, which came after Israel struck the Iranian embassy in Syria on 1 April.

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