Iran's news agency says explosions were heard in the central province of Isfahan on Friday. The country's state-run media outlets say key facilities, including nuclear-related sites, in the region were not damaged.

The Fars news agency said that the cause of the sounds is unknown. The explosions were reportedly heard in an area in the province's northwest that is near the Isfahan airport and an Iranian air force base.

Another Iranian media outlet, Mehr news agency, reported that the blasts heard in Isfahan were the sounds of three drones being shot down. But it said that details, such as where the drones came from, are unknown. It said that there was no damage at the air force base in Isfahan.

Iran's state-run news agency said no large-scale airstrikes have been reported and no interceptions have been made using missile defense systems.

Iran's state-run television has reported that passenger plane services, which had been suspended at several airports in the country, have resumed.

US media outlets have cited US government officials as saying that Israel attacked Iran.

ABC News quoted a senior government official as saying that Israel fired missiles in retaliation for Iran's massive attack on Israel.

CNN cited a government official as saying that Israel's attack was not targeted at Iran's nuclear-related sites.

Israel had threatened to take retaliatory measures in response to Iran's large-scale missile and drone attack on Saturday through Sunday.

But it is not yet known if Israel is connected to the explosive sounds heard in Isfahan on Friday.