ABC, CBS and CNN, among other media, reported the strikes early Friday Middle East time, quoting US officials. There was no immediate comment from the White House.

The Pentagon duty desk said in response to a query from AFP: "We do not have anything to offer at this time."

Iran activated its air defense system over several cities, state media reported, after the country's official broadcaster said explosions were heard near the central city of Isfahan.

Israel warned it would hit back after Iran fired hundreds of missiles and drones at its arch foe over the weekend. Most of them were intercepted.

That strike came in the wake of an attack on Iran's consulate in Damascus widely blamed on Israel.