Iranian state media reports explosions heard at airport in central Iran

Iranian state media has reported that explosions have been heard at Isfahan airport in central Iran, amid conflicting reports from US and Iranian officials about what caused them.

Sources told the FARS news agency that the country's air defence system has been activated in Isfahan province against "an object suspected to be a drone".

"The sound of three explosions has been heard near an army base in north-west Isfahan," the sources reportedly said.

"At around 12:30am GMT (10:30am AEDT), three drones were observed in the sky over Isfahan. The air defence system became active and destroyed these drones in the sky," Iranian state TV added.

A senior commander of Iran's army, Siavosh Mihandoust, said, according to state TV, that no damage was caused in the overnight attack.

It comes as a United States official told US broadcaster ABC that missiles were fired by Israel.

This assertion was disputed by an Iranian official who told Reuters that the explosions heard in Isfahan were a result of Iran firing its air defence batteries.

The Iranian official added that no missile attack was carried out against Iran.

The US official could not confirm whether Syria and Iraq were hit as well, after initial reports that explosions were also heard at those sites.

The Israeli military said that warning sirens which sounded early on Friday in northern Israel were a false alarm. 

Flight tracking websites have shown multiple flights have been diverted away from Iranian airspace. 

Dubai-based carrier Flydubai confirmed in a statement it had cancelled all flights to the Iranian capital Tehran on Friday and had turned back a flight due to the closure of the airport.

International flights into the Imam Khomeini International Airport have been cancelled until 7am GMT (6pm AEDT), according to Iranian news agency Mehr.

Iranian state media also reports that flights over Isfahan, Shiraz and Tehran cities have been "suspended".

Flights were seen diverting away from Iran's Isfahan province.(Supplied: Flightradar24)

According to Reuters, several Iranian nuclear sites are located in Isfahan province, including Natanz, which is considered the centrepiece of Iran's uranium enrichment program.

Iran's state TV said the nuclear sites remain unharmed.

Over the weekend, Iran launched hundreds of drones and missiles in a retaliatory strike after a suspected Israeli strike on its embassy compound in Syria.

Most of the drones and missiles were downed before reaching Israeli territory.

Israel had said it was going to retaliate against Iran's April 13 missile and drone attack.

ABC/wires