US President Donald Trump and his intelligence chiefs have played down a security breach that saw a journalist invited into a Signal group chat where he reported seeing national security officials plan airstrikes in Yemen.

US Director of National Intelligence Tulsi Gabbard and CIA Director John Ratcliffe denied at a Senate hearing that any classified information was shared in the message chain. Defence Secretary Pete Hegseth also faced scrutiny for the messages, though he did not testify.

Democrats on the panel rebuked the cabinet members as "incompetent" with national security.

Over at the White House, Trump stood by National Security Adviser Mike Waltz, who was at the centre of the leak.