A US Navy admiral testified that Defence Secretary Pete Hegseth did not give the order to kill them all during a controversial second US military strike on an alleged drug boat in the Caribbean, multiple lawmakers have said.

The affirmations by Democratic and Republican lawmakers were made after viewing footage of the 2 September double-strike incident and hearing from Adm Frank Bradley in closed-door hearings.

The briefing before members of the House of Representatives and later the Senate came as questions continued around the legality of military force used against suspected drug boats.

The White House has said Adm Bradley was responsible for the strikes and that he acted within the law.

Adm Bradley did the right thing, said Democratic congressman Jim Himes, the ranking member of the House Intelligence Committee, after he heard from the admiral and viewed the video.

But what I saw in that room was one of the most troubling things I've seen in my time in public service, Himes said.

Yes, they were carrying drugs. They were not in the position to continue their mission in any way, he added.

After the briefing, Representative Adam Smith, the highest-ranking Democrat on the House Armed Services Committee, released a joint statement with Himes calling for the video to be released publicly.

The briefing left us with more questions than answers, and Congress must continue to investigate this matter and conduct oversight, they said.

Republican Senator Tom Cotton, chair of the Senate Intelligence Committee, said Adm Bradley and Hegseth did exactly what we would expect them to do.

He saw two survivors trying to flip a boat loaded with drugs bound to the United States back over so they could stay in the fight.

The incident has drawn scrutiny as the legality of targeting wounded combatants remains in question.

US President Donald Trump has stated he has no problem with the footage being made public. In the aftermath of the strikes, concerns over US military conduct and the ongoing campaign against drug traffickers continue to intensify.