US broadcaster ABC News reported that Israeli missiles hit a base in Iran, citing an unnamed senior US official.
Iranian state television reported the explosions in Isfahan as air defenses were activated and flights were grounded in several areas, including Tehran and Isfahan.
There are no reports of casualties. There was no official response from Iran either.
Israel vowed to respond after Iran launched a barrage of drones and missiles on the country last Saturday, after a suspected Israeli attack on Iran's embassy compound in Damascus killed a top commander.
Bombings were also reported in Syria and Iraq.
The US and many European countries are calling on Israel not to respond to the Iranian attack.
Isfahan is considered a strategically important city and hosts several important sites including military research and development bases and bases. The nearby city of Natanz is one of Iran's nuclear enrichment sites.
Commercial planes began diverting their routes over western Iran early Friday after Iran's semi-official Fars news agency said it heard « explosions » over the city of Isfahan.
