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.

On Thursday evening the US military posted on X that it had killed four people in another boat strike in the eastern Pacific Ocean, at Hegseth's direction.

Prior to news of the latest strike, lawmakers reacted to the testimony, with the most senior Democrat on the House intelligence committee, Jim Himes, saying Adm Bradley had his respect and should have the respect of all of us.

He added: But what I saw in that room was one of the most troubling things I've seen in my time in public service.

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

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.

Senator Jack Reed, a Democrat, said in a statement he was disturbed by what he saw, adding that his party would continue to investigate the incident.

The revelation there were two strikes when the first left survivors has raised new questions over the legality of the administration's deadly ongoing campaign against boats, due to what the rules of conflict say about targeting wounded combatants.

The incident and its implications for international law and military ethics remain at the forefront of political discussions, as questions regarding the legality and morality of such military actions persist.