US President Donald Trump's national security adviser Mike Waltz will leave his post after a scandal in which a journalist was accidentally included in a chat between officials about air strikes in Yemen.

Waltz and his deputy Alex Wong are stepping down, CBS News reported. According to Fox News, Trump will comment on the matter soon.

The former congressman is the first senior official to leave Trump's administration in his second term, which has so far been more stable than the first in terms of personnel changes.

Waltz was under pressure after the editor-in-chief of The Atlantic magazine revealed in March that Waltz had mistakenly added him to a chat on the Signal messaging app about attacks on Yemeni Houthis.

From there, the plan for the attack was leaked, including the time when US military aircraft would take off to bomb targets in Yemen, with the first messages sent just half an hour before takeoff.

Defense Secretary Pete Hageet is also under pressure over the scandal. | BGNES