President Donald Trump said the United States had attacked a vessel he said was carrying drugs in the US Southern Command's area of responsibility, the latest US strike in the region.

Friday's strike – at least the third against alleged drug vessels – comes amid a large US military buildup in the southern Caribbean. Five F-35 aircraft were seen landing in Puerto Rico on Saturday after the Trump administration ordered 10 of the stealth fighters to join the buildup.

Hours earlier, Venezuela accused the United States of waging an "undeclared war" in the Caribbean and called for a UN probe of American strikes that have killed over a dozen alleged drug traffickers on boats in recent weeks.

"It is an undeclared war, and you can already see how people, whether or not they are drug traffickers, have been executed in the Caribbean Sea. Executed without the right to a defence," Defence Minister Vladimir Padrino Lopez said as he attended a military exercise in response to the US "threat".

In a post on Truth Social on Friday, Trump said the Pentagon carried out the strike on his orders, killing "3 male narcoterrorists aboard the vessel".

He added: "Intelligence confirmed the vessel was trafficking illicit narcotics, and was transiting along a known narcotrafficking passage enroute to poison Americans."

The US Southern Command is the military's combatant command that encompasses 31 countries through South and Central America and the Caribbean.

Trump did not provide evidence but did post a minute-long aerial video that showed two side-by-side videos of a vessel, one in colour and one in black and white, as it moved through the water. About halfway through, the vessel appears to be struck by at least one projectile and then explodes. The video ends with a single aerial angle of the vessel on fire in the water.

Trump did not say where the vessel departed from or where specifically the strike took place.

In addition to the F-35s, there are at least seven U.S. warships in the region, as well as one nuclear-powered submarine.

The US military carried out a strike earlier this week in the Southern Caribbean that targeted an alleged Venezuelan drug cartel vessel heading to the United States.

The Trump administration has provided scant information about the first two strikes, despite demands from US lawmakers that the government justify the action. Trump said the first strike, on September 2, struck a vessel allegedly carrying members of Venezuelan gang Tren de Aragua.

The Venezuelan government, which says it has deployed tens of thousands of troops to fight drug trafficking and defend the country, has said none of the people killed in the first strike belonged to Tren de Aragua.

Venezuelan President Nicolas Maduro has repeatedly alleged the United States is hoping to drive him from power. Washington last month doubled its reward for information leading to Maduro's arrest to US$50 million, accusing him of links to drug trafficking and criminal groups, which Maduro denies. (Reuters/AFP)