A strike on an alleged drug-trafficking boat in the eastern Pacific Ocean killed four people on Thursday, the US military said, amid a growing controversy over a campaign that has taken more than 87 lives.

Defense Secretary Pete Hegseth and President Donald Trump's administration have especially come under fire over an incident in early September in which US forces targeted the wreckage of a vessel that had already been hit, killing two survivors.

A senior Democratic lawmaker who saw footage of that incident on Thursday said it showed a US attack on "shipwrecked sailors," while others have described it as a possible war crime.