It was unclear if the country came under attack, as no Iranian official directly acknowledged the possibility and Israel's military did not respond to a request for comment.
However, tensions have been high since the Saturday retaliatory assault on Israel amid its war on Gaza and its own strikes targeting Iran in Syria.
Air defence batteries fired in several provinces over reports of drones being in the air, state television reported.
In particular, IRNA said air defences fired at a major air base in Isfahan, which long has been home to Iran's fleet of American-made F-14 Tomcats — purchased before the 1979 Islamic Revolution.
Tasnim 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.
“At 4:45, we heard gunshots. There was nothing going on,” he said. “It was the air defence, these guys that you’re watching, and over there too.”
The facility at Isfahan 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.
State television described all atomic sites in the area as “fully safe."
The United Nations' nuclear watchdog, the International Atomic Energy Agency, also said “there is no damage to Iran’s nuclear sites” after the incident.
General Siavosh Mihandoost, a local army commander, also told state TV the incident caused “no damage” around Isfahan.
Iran's nuclear program has rapidly advanced to producing enriched uranium at nearly weapons-grade levels since the collapse of its atomic deal with world powers after then-President Donald Trump withdrew America from the accord in 2018.
US officials declined to comment as of early Friday, but American broadcast networks quoting unnamed US officials said Israel carried out the attack. The New York Times quoted anonymous Israeli officials claiming the assault.
Speaking during a press conference following a Group of Seven foreign ministers’ meeting in Capri, US Secretary of State Antony Blinken avoided answering questions about the strikes on Iran
However, he repeated that the US was "not involved" in any offensive military operations and is continuing to work for de-escalation.
"All I can say is that for our part and for the entire G7, our focus has been on de-escalation and on avoiding a larger conflict. Actually that's been true since day one and the horrific events of October 7. A big part of our approach has been to prevent the conflict from spreading to avoid escalation everywhere."
"Those efforts will continue," Blinken added.
Italy's Foreign Minister Antonio Tajani said the US government was informed at the "very last minute" by Israel about the attack and states "there was no involvement" from Washington.
Diverting flights
Dubai-based carriers Emirates and FlyDubai began diverting around western Iran at about 4:30 a.m. local time. They offered no explanation, though local warnings to aviators suggested the airspace may have been closed.
Iran then grounded commercial flights in Tehran and across areas of its western and central regions. Loudspeakers informed customers of the incident at Imam Khomeini International Airport in Tehran, online videos purported to show. Iran later restored normal flight service, authorities said.
Hossein Dalirian, a spokesperson for an Iranian government cyberspace agency who as a journalist had ties to Iranian defence officials, said on the social media platform X that several small “quadcopter” drones had been shot down. A state television reporter in Isfahan said the same in a live report, saying “several small drones were flying in the sky over Isfahan, which were fired at.”
Previous Israeli attacks have targeted Isfahan's nuclear and military sites.
In January 2023, Iran blamed Israel for an attack on a what it called a “workshop complex” in the centre of Isfahan city, which it said involved three drones and caused minor damage.
Israeli Prime Minister Benjamin Netanyahu said at the time that his country had been “taking action against certain weapons development" in Iran, but he neither confirmed nor denied involvement.
In April 2021, Iran accused Israel of being behind an explosion at the Natanz uranium enrichment site, also in the Isfahan province, that damaged a large number of centrifuges. Israeli media reported at the time that it was an operation by the Mossad intelligence agency.
Syria again
Around the time of the incident in Iran, Syria's state-run SANA news agency quoted a military statement saying Israel carried out a missile strike targeting an air defence unit in its south and causing material damage.
The Britain-based Syrian Observatory for Human Rights, an opposition war monitor, said the strike hit a military radar for government forces. It was not clear if there were casualties, the Observatory said.
That area of Syria is directly west of Isfahan, some 1,500 kilometres (930 miles) away, and east of Israel.
Meanwhile in Iraq, residents of Baghdad reported hearing sounds of explosions, but the source of the noise was not immediately clear.
The incident Friday in Iran also sparked concerns about the conflict again escalating across the seas of the Middle East, which have been seeing attacks by the Houthi rebels of Yemen on shipping over the war in Gaza, in support of the Palestinians.
The British military's United Kingdom Maritime Trade Operations centre warned ships in the region that they could see increased drone activity in the skies.
“There are currently no indications commercial vessels are the intended target,” it wrote.
The Houthis have launched at least 53 attacks on shipping related to Israel, seized one vessel and sank another since November, according to the US Maritime Administration.
Houthi attacks have dropped in recent weeks as the rebels have been targeted by a US-led airstrike campaign in Yemen and as shipping through the Red Sea and Gulf of Aden has declined over the threat.
However, Iranian state-run media sought to downplay the incident after the fact, airing footage of an otherwise peaceful Isfahan morning.
Russia has made clear to Israel that Iran "does not want escalation," Moscow's Foreign Minister Sergei Lavrov said Friday.
"There have been telephone contacts between the leadership of Russia and Iran, our representatives and the Israelis. We made it very clear in these conversations, we told the Israelis that Iran does not want escalation," Lavrov said in an interview with Russian radio stations.
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