An Israeli missile has struck Iran, US officials inform CBS News, a partner station of the BBC.

The Iranian state media reported, according to Reuters, that explosions were heard in the central province of Isfahan and that commercial flights over Iran's major cities, including Isfahan, Shiraz, and Tehran, were halted. However, later, flights at Mehrabad International Airport and Imam Khomeini International Airport in Tehran have resumed, according to Iran's official news agency, IRNA.

The “strong sounds heard in several regions of the country were a result of air defence being activated to counter several unidentified mini-drones,” according to Iran's state broadcaster IRIB, citing "reliable sources".

Tasnim news agency, closely affiliated to the IRGC, has published this video with the caption: "Isfahan's nuclear site is completely safe". pic.twitter.com/rHAxJmGGuJ
— Ghoncheh Habibiazad | غنچه (@GhonchehAzad) April 19, 2024

Iranian state TV said that three drones were seen flying over the city of Isfahan at around 12:30GMT. The drones were then destroyed when the nation's air defense system was triggered, according to Reuters.

Iran is on high alert following Israel's declaration on Saturday night that it would retaliate against an Iranian attack.

Several provinces in the nation have activated their air defense systems, according to state news agency IRNA. According to IRNA, the nation activated its "air defense batteries."

The National Center of Cyberspace of Iran's spokesperson has categorically denied any missile attack. "There has been no air attack from outside borders to Isfahan or other parts of the country," Hossein Dalirian wrote on X.

Here is 🇮🇷 #Iran's state broadcaster in Isfahan this morning:
"The city is in complete calm and security, people are going on with their normal lives."
"1-2 hours ago, sounds were heard in the sky. We understand several miniature UAVs were overhead, which were shot down."… pic.twitter.com/nSuesaml6R
— Marwa Osman || مروة عثمان (@Marwa__Osman) April 19, 2024

He said Israel had "only made a failed and humiliating attempt to fly quadcopters [drones] and the quadcopters have also been shot down".

Iranian state media cited an army general in the Isfahan province as saying that no damage has been reported. "The strong sound heard in Isfahan was due to air defence firing at suspicious objects. There's been no damage,” he says.

Iranian media stated that all nuclear facilities are safe and has not reported any direct effects. The Israeli army has refrained from commenting.

The province of Isfahan is home to multiple nuclear sites, a sizable air base, and a significant missile production facility.

The BBC Persian Instagram account shared a video from Isfahan that features orange flashes in the night sky accompanied by what sound like anti-aircraft gunfire bursts.

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A post shared by BBC NEWS فارسی (@bbcpersian)

Iranian officials had threatened to retaliate quickly to any Israeli attack on their country in recent days. The international community has made calls for moderation in an effort to defuse the situation.

UN Secretary General António Guterres declared on Thursday that there had been a "perilous escalation" in hostilities between Iran and Israel.