Iran's semi-officials Fars news agency reported that explosions were heard near an airport in the central city of Isfahan early on Friday morning.
"The cause of these sounds is still unknown, and investigations continue until the exact details of the incident are determined," Fars wrote.
Meanwhile, at around the same time, ABC News cited an unnamed US official as saying that Israeli missiles had hit a site in Iran.
Israel had threatened to retaliate after Iran launched drones and missiles at its airspace over the weekend.
Isfahan is Israel's third most populous city and a major industrial hub. It's also home to an Iranian airbase, and sites associated with Iran's nuclear program.
Flights diverted, Iranian state media says air defenses activated
State-run Iranian news agency and others in Iran soon also reported the sound of an explosion in Isfahan province.
It said that air defense systems had been activated in several Iranian provinces.
IRNA also reported restrictions on commercial flights in Iranian airspace.
Dubai-based carriers Emirates and FlyDubai began diverting around western Iran about 4:30 a.m. local time. They offered no explanation, though local warnings to aviators suggested the airspace may have been closed.
Iranian official says drones 'shot down,' with no sign of missile strike
The head of Iran's space agency, Hossein Dalirian, wrote online that reports in US media of an Israeli strike on Iran were exaggerated.
He said that several small drones "have been successfully shot down by the country's air defense," and that to his knowledge there had been "no missile attack for now" on the country.
Dalirian's posts addressed the issue as being a routine one for Iran's air defenses, describing it as a "failed and humiliating attempt" to attack with "quadcopters."
The reports on Iranian news agencies including Fars and IRNA of explosions being heard near the Shekari army airbase near Isfahan grabbed instant attention given the tensions between Israel and Iran in recent weeks.
US received advance notice of Israel's reported Iran strike: Media
US media have said that the United States was informed beforehand that Israel was intending to launch an attack on Iran.
US broadcasters NBC and CNN cited sources familiar with the matter and a US official respectively in their reports.
According to CNN, the official said Washington had not endorsed the reported Israeli operation.
It quoted the official as stating the target was not a nuclear facility.
Australia tells its nationals to leave Israel, Palestinian territories if possible
Australia has told its citizens to leave Israel or the Palestinian territories "if it's safe to do so."
A travel advisory on Friday said there was a "high threat of military reprisals and terrorist attacks ... across the region."
Australian citizens had previously been told to reconsider their need to travel to both areas.
In a travel advisory update, the Department of Foreign Affairs warned: "Military attacks may result in airspace closures, flight cancellations and diversions and other travel disruptions."
"Tel Aviv's Ben Gurion International Airport may pause operations due to heightened security concerns at any time, and at short notice," it said.
Australia distinguishes between lower-risk areas in Israel and higher-risk border areas and the Palestinian territories.
"We continue to advise reconsider your need to travel overall due to the volatile security situation including the threat of terrorism, armed conflict, and civil unrest."
"We continue to advise do not travel to Gaza, border areas with Gaza, border areas with Lebanon closed by Israeli authorities and the West Bank [excluding East Jerusalem], due to the volatile security situation."
US embassy in Israel restricts movement of staff
The United States embassy in Israel on Friday issued a security alert warning employees and their family members of restrictions to personal travel in a number of areas.
"Out of an abundance of caution following reports that Israel conducted a retaliatory strike inside Iran, US government employees and their family members are restricted from personal travel outside the greater Tel Aviv (including Herzliya, Netanya, and Even Yehuda), Jerusalem, and Be’er Sheva areas until further notice," the US embassy said.
The security advisory went on to say that US citizens were reminded "of the continued need for caution and increased personal security awareness as security incidents often take place without warning."
The advisory added: " The security environment remains complex and can change quickly depending on the political situation and recent events."
IAEA confirms 'no damage' to Iran's nuclear sites
Nuclear watchdog, the International Atomic Energy Agency (IAEA), said on Friday that there had been no damage at Iranian nuclear facilities following earlier reports of explosions.
"IAEA can confirm that there is no damage to Iran's nuclear sites," the agency said on social media platform X, formerly Twitter.
The IAEA went on to say that its chief Rafael Grossi "continues to call for extreme restraint from everybody and reiterates that nuclear facilities should never be a target in military conflicts."
Iranian media reported that there had been explosions near Qahjavarestan, near Isfahan airport and the 8th Shekari army airbase.
Iran's Tasnim news agency reported that nuclear facilities in Isfahan were "completely secure."
What we know about Isfahan's nuclear facility
The nuclear facility at Isfahan which is located in central Iran, operates three small Chinese-supplied research reactors.
It also handles fuel production and other activities for Iran's civilian nuclear program.
In February Iran announced that it was building a fourth research reactor in Isfahan, which state media reported would have a variety of applications, including fuel and nuclear material tests.
The country's nuclear program has been criticized internationally with experts outside of the country concerned that the program ultimately seeks to build nuclear weapons.
Iran contends it has no such intentions and that its nuclear program is for civilian use only.
Isfahan is also home to the subterranean Natanz enrichment site, which has been the repeated target of sabotage.
