Trump says Iran shot down US helicopter and vows to respond

President Donald Trump has accused Iran of shooting down a US helicopter over the Strait of Hormuz and vowed to respond to the attack out of "necessity".

Two crew members of the Apache helicopter that crashed following the attack were rescued by an American sea drone, the Pentagon said in a statement.

"There were two pilots involved, both are safe and uninjured," Trump wrote on Truth Social. "Nevertheless, the United States must, of necessity, respond to this attack."

It was not immediately clear what the US response would be, but any military action risks inflaming the shaky ceasefire with Iran once again. There has been no immediate response from Tehran on the US president's comments.

Iranian media appeared to acknowledge the incident, with the semi-official Mehr News Agency reporting that Iran had not claimed responsibility.

The prospect of US military action against Iran has emerged as Israeli forces carried out strikes across southern Lebanon on Tuesday.

Tehran had warned that Israeli attacks on southern Lebanon would trigger another wave of retaliatory strikes.

Iran's Foreign Minister Abbas Araqchi said on Tuesday that foreign forces near Iran's territory were at "constant risk on account of their own human errors, plain accidents or potentially being caught in crossfire".