Trump branded Petro a "thug" and suggested he was a drug trafficker leading his country to ruin, prompting the leftist leader to vow: "I will defend myself legally with American lawyers."

Trump said vital military aid to Colombia had been cut and warned Petro to "watch it," hours after Defense Secretary Pete Hegseth posted a video of a boat engulfed in flames.

"There were two narco-terrorists aboard the vessel... Both terrorists were killed and no US forces were harmed," Hegseth wrote on X, adding: "Just as Al-Qaeda waged war on our homeland, these cartels are waging war on our border."

He vowed that there would be "no refuge or forgiveness."

The strike, apparently carried out in international waters, brings the total number of such US attacks to at least eight, with 34 people dead, according to US figures.

Washington has deployed stealth warplanes and Navy ships as part of what it calls counter-narcotics efforts, but has yet to release evidence that its targets were drug smugglers.

The Pentagon told Congress the United States is in "armed conflict" with Latin American drug cartels, designating them as terrorist groups and describing suspected smugglers as "unlawful combatants."

Experts say the summary killings are illegal even if they target confirmed traffickers.

Regional tensions have flared, with Colombia recalling its ambassador to Washington and Venezuela accusing the United States of plotting to overthrow President Nicolas Maduro.

The origin of the targeted vessels -- seven boats and one semi-submersible -- has not been disclosed, though some were destroyed off Venezuela's coast.

At least one came from Trinidad and Tobago, another from Colombia, families of the deceased in those countries have told AFP.

Colombia is the world's top cocaine producer, but has long worked alongside the United States to curb production, which is controlled by a range of well-funded paramilitary, cartel and guerrilla groups.

But relations have soured markedly since Trump and Petro have taken power.

Petro on Wednesday blasted "slanders that have been thrown at me in the territory of the United States by high-ranking officials," but said: "When our help is needed to fight drug trafficking, US society will have it."