Iran's state media reported explosions in the central province of Isfahan on Friday, as US media quoted officials saying Israel had carried out retaliatory strikes on its arch-rival.
Air defence systems over several Iranian cities were activated, state media reported, after the country's official broadcaster said explosions were heard near the city of Isfahan.
Israel had previously warned it would retaliate after Iran fired hundreds of missiles and drones at Israel almost a week ago, in retaliation for a deadly strike -- which Tehran blamed on its foe -- that levelled Iran's consular annex at its embassy in Syria.
There had been no reaction from Israeli or Iranian officials to the overnight strikes and the extent of the damage remained unclear.
Israeli strikes also "targeted a radar installation of the Syrian army" in the country's south, according to the Syrian Observatory for Human Rights war monitor.
Israel's attack has deepened fears of its war on Gaza escalating into an all-out regional conflict, with UN Secretary-General Antonio Guterres warning on Thursday that "the Middle East is on a precipice" and calling for restraint from all parties.
Israel has faced growing global opposition to the relentless war that has reduced much of Gaza to rubble, while its 2.4 million people have suffered under an Israeli siege that has blocked most water, food, medicines and other vital supplies.
