President Donald Trump's administration is facing a scandal over the accidental leak of a group chat by senior security officials on the strikes, which targeted Yemen's Huthi rebels in a bid to curb their attacks on commercial shipping and military vessels in the Red Sea and Gulf of Aden.

The probe will evaluate "the extent to which the Secretary of Defense and other DoD personnel complied with DoD policies and procedures for the use of a commercial messaging application for official business," said the memo from the acting inspector general, Steven Stebbins.

"Additionally, we will review compliance with classification and records retention requirements," according to the memo, which said the investigation is in response to a request from the top two members of the Senate Armed Services Committee, a Republican and a Democrat.

The Atlantic magazine revealed last week that its editor -- a well-known US journalist -- was inadvertently included in the Signal chat in which officials including Trump's National Security Advisor Mike Waltz and Hegseth discussed details of air strike timings and intelligence.