US lawmakers are pressing the Trump administration for answers about military strikes on suspected Venezuelan drug boats, following reports that a follow-up strike was ordered to kill survivors of an initial attack.

Republican-led committees overseeing the Pentagon have vowed to conduct "vigorous oversight" into the US boat strikes in the Caribbean, following the report.

On Friday, The Washington Post reported that a US strike on a boat on 2 September left two survivors, but a second attack was carried out to comply with Defence Secretary Pete Hegseth's orders to "kill everybody" on board.

Hegseth decried the report as "fake news" and President Donald Trump said he believed him "a 100%".

The US has expanded its military presence in the Caribbean and carried out a series of lethal strikes on suspected drug-smuggling boats in international waters off Venezuela and Colombia, as part of what it calls is an anti-narcotics operation.