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Israel has carried out a strike inside Iran, a US official says, a move that threatens to push the region deeper into conflict.
The target is not nuclear, the official said.
Iran's air defence systems were activated in several locations after three explosions were heard close to the airport and an army base in the Iranian city of Isfahan, state media reported early this morning.
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Three explosions were heard near a military base where fighter jets are located in the north-west part of Isfahan, Iran's semi-official FARS news agency reported.
The cause of the explosions is still unknown.
"The defence is activated in response to an object that is likely to be a drone," sources told FARS news.
The news agency reported that a possible target of the blast was a military radar and that the explosion broke several windows of office buildings in the area.
It comes as tensions remain heightened in the Middle East after a decades-long shadow war between Israel and Iran erupted into the open this month and sent fear of a wider conflict coursing through the region.
Iran's state news agency, IRNA, reported the country's air defence systems have been activated in several provinces of the country.
Outgoing flights from several Iranian airports have been cancelled, according to an Iranian official, Iranian state media Press TV reported.
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Flights heading to "Tehran, Isfahan and Shiraz, the airports of the West, North West and South West have been suspended" the director of public relations for an Iranian airport company told state-run Mehr TV.
Flight tracking website Flight Radar 24 showed that multiple flights were diverted over Iranian airspace early Friday.
CNN counted at least eight flights.
FARS reported that the explosion was heard in the city of Ghahjaworstan, north-west of Isfahan, citing local sources.
Ghahjaworstan is located near Isfahan Airport and "the eighth hunting base of the Army Air Force", according to FARS.
Iranian Press TV also reported that an explosion was heard "near Iran's central city of Isfahan", adding the cause of the blast was not yet known.
Reports of the explosion come hours after Iran's Foreign Minister Hossein Amir-Abdollahian told CNN that if Israel takes any further military action against Iran, its response would be "immediate and at a maximum level".
His remarks come in the wake of an unprecedented Iranian attack on Israel last week that Tehran said was retaliation for a deadly suspected Israeli airstrike on Iran's consulate in Syria – placing the region on edge as Israel vowed to strike back in return.
More to come.
