The United States has launched “major combat operations” against Iran, President Donald Trump said on Saturday, vowing to "annihilate" the country's navy and missile sites, and urging Iranians to overthrow their government.

In a video address after the United States and Israel started bombing Iran, Trump made clear the goal was destruction of the Islamic republic's military and toppling of the authorities in power since the 1979 revolution.

"We are going to destroy their missiles and raze their missile industry to the ground. It will be totally, again, obliterated. We're going to annihilate their navy," Trump said in the address from his Florida home posted to his Truth Social platform.

Speaking to Iranians, Trump said: "When we are finished, take over your government. It will be yours to take."

"This will be probably your only chance for generations," Trump said. "The hour of your freedom is at hand."