Iran has denied that an Israeli attack has hit its notorious “nuclear energy mountain” near Isfahan after local air defences were triggered and multiple explosions were heard by residents.

Blasts were reported for half an hour near a major air base and a nuclear site in Isfahan early on Friday morning, although it was not immediately clear what – if any – damage had been done.

The International Atomic Energy Agency said on Friday there had been no damage to Iran’s nuclear sites but that it was monitoring the situation closely.

The US confirmed Israel had struck Iran but did not give any further details. US officials told CBS News that Israel had hit Iran with a missile but did not say where or what the impact was.

Washington is understood to have been warned in advance but did not endorse the plan or help with it.

Israel has been warning that it would respond to a major Iranian attack last weekend that involved more than 300 drones, rockets and missiles, despite calls from its Western allies to avoid any further escalation.

Israel’s military refused to comment when asked about the developments on Friday morning.

Tensions in the Middle East have soared in the past few weeks. Tehran’s attack was in turn a response to a suspected Israeli strike on Iran’s Damascus consulate, which killed a senior Islamic Revolutionary Guard Corps general.

The fact that Tehran is downplaying the assault suggests it may be looking to avoid further escalation, according to experts.

Iranian state TV described Friday’s attack as “psychological warfare”, saying that it had intercepted several drones but that all sites in Isfahan were “fully safe”.

“Nuclear centres are not harmed,” said state TV as it reported on the blasts.

“Three small drones were spotted in the skies above Isfahan and around the Zareanjan area at approximately 4am,” the semi-official Mehr news agency reported, citing an unnamed course.

“Following the siting of these micro-drones, the air defence system was activated, destroying these drones.”

No damage was caused in the overnight attack, Siavosh Mihandoust, a senior commander of Iran’s Army, said on Friday according to state TV.

“The sounds were related to Isfahan air defence shooting at suspicious objects and we have not had any damage or accident,” said Colonel Mihandoust.

State television also acknowledged “loud noises” in the Isfahan area.

“At 4.45, we heard gunshots. There was nothing going on,” a reporter said. “It was the air defence, these guys that you’re watching, and over there too.”

State TV IRNA said air defences had been activated at a major air base in Isfahan, which has long been home to Iran’s ageing fleet of American-made F-14 Tomcats – purchased before the 1979 Islamic Revolution.

Tasnim, a semi-official news agency in Iran associated with the Islamic Revolutionary Guard Corps, later published a video from one of its reporters who said he was in the southeastern Zerdenjan area of Isfahan, near its “nuclear energy mountain”.

The footage showed two different anti-aircraft gun positions, and details of the video corresponded with known features of the site of Iran’s Uranium Conversion Facility at Isfahan.

The facility operates three small Chinese-supplied research reactors, as well as handling fuel production and other activities for Iran’s civilian nuclear program.

Isfahan is also home to sites associated with Iran’s nuclear program, including its underground Natanz enrichment site, which has been repeatedly targeted by suspected Israeli sabotage attacks.

‘The sky became orange’

Residents in the central city told The Telegraph they were woken up first by buzzing sounds and then explosions.

“I rushed out as I was worried about any attack in recent days. and then I saw a big boom and then a few more small ones and the sky became orange,” Ali, a resident of the eastern part of Isfahan, said in a telephone interview.

“We hear these sounds usually as they test air defence systems regularly, but this one was more than that and too early,” he added.

“For around half an hour, there was the sound and light of shots going up from the mountain and then small explosions in the sky.”

Another resident said he was fleeing the city as a precaution.

“I was doing my morning prayer when I heard shots and explosions,” said Misaq.”It went on for over half an hour. There were several explosions over the mountain.

“Everything looks normal now, but I cannot risk the safety of my family. I’m driving now and leaving Isfahan. I will be back if it is calm tomorrow.”

Sounds of explosions were also heard in northwestern Tabriz, with IRNA reporting the same line: that air defence systems were activated after “suspicious objects” were spotted.

Flights in Tehran, Isfahan and Shiraz were suspended for over two hours. The country’s civil aviation authority later reported the flights were back to normal by early Friday.

On Thursday Iran threatened to build a nuclear bomb and hit Israel’s nuclear facilities if it was attacked by Benjamin Netanyahu’s forces.

But Holly Dagres, a senior fellow at the Atlantic Council’s Middle East Programs, said the reaction from Iran suggested a retaliatory strike was not imminent.

“Tehran is trying to downplay the Israeli response, as evidenced by the coverage by state media, which attempted to show that all was ‘safe and calm’,” she told The Telegraph.

“However, citizen journalist footage of air raid sirens going off and air defence responding in Isfahan suggests this was not some minor event.”

“This downplaying of events by Tehran may actually be a tactic to prevent them from feeling the need to retaliate directly against Israel again,” she said.

“In essence, this could potentially be a restoration of deterrence.”