Israel has issued a nationwide warning to head to shelters after Iran launched missiles.

The warning came after the U.S. and Israel launched an attack on Iran.

The U.S. and Israel launched an attack Saturday on Iran, with the first apparent strike happening near the offices of Supreme Leader Ayatollah Ali Khamenei.

Iranian media reported strikes nationwide, and smoke could be seen rising from the capital.

President Donald Trump said in a video posted on social media that the U.S. had begun "major combat operations in Iran." He claimed Iran has continued to develop its nuclear program and plans to develop missiles to reach U.S. and appealed to the Iranian people to "take over your government - it will be yours to take."

Trump acknowledged that there could be American casualties following Iran strikes, saying "that often happens in war."

It wasn't immediately clear whether the 86-year-old Khamenei was in his offices at the time of the strike. He hasn't been seen publicly in days as tensions with the United States have grown.