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 said on X, adding: "Just as Al-Qaeda waged war on our homeland, these cartels are waging war on our border."

Tuesday's 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.

Until now the strikes had only taken place in the Caribbean.

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 those killed told AFP.

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.

Colombia is the world's top cocaine producer, but has worked for decades 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.

- 'Unacceptable' -

"Under no circumstances can one justify that kind of threats and accusations that have no basis whatsoever," Colombian ambassador Daniel Garcia-Pena told AFP after being recalled to Bogota for consultations.

"There are elements that are unacceptable," he said, visibly alarmed after being told what Trump had said minutes before.

"We are facing a US government that is trying to change the paradigm of its international relations" Garcia-Pena added, "where uncertainty unfortunately plays a very important role."

"At stake here is a historic relationship of more than 200 years that benefits both the United States and Colombia," he said.