US airstrikes on alleged drug-trafficking boats in the Caribbean Sea are an "act of tyranny", Colombia's President Gustavo Petro told the BBC in an interview where he also called for criminal proceedings against US officials if investigations find Colombians were killed in the attacks.

President Donald Trump has cast the strikes, which have reportedly killed 17 since they began this month, as needed to stop the flow of fentanyl and other illegal narcotics into the US.

Legal experts and lawmakers, though, have questioned if they violate international human rights laws.

"Why launch a missile if you could simply stop the boat and arrest the crew?" said Petro. "That's what one would call murder."

Speaking to the BBC on Wednesday, Petro said there should be "zero deaths" in stopping speedboats believed to be involved in drug smuggling.

"We have a long history of collaborating with American agencies and other agencies of carrying out maritime seizures of cocaine," he said. "No one has ever died before. There is no need to kill anyone."

He added that the principle of the proportionality of force is violated "if you use anything more than a pistol".

The strikes in international waters have primarily focused on Colombia's neighbour Venezuela, according to the Trump administration, but the US has provided little details about the targets and the individuals killed, and its reports that members of the Tren de Aragua gang were on the first attacked boat are in dispute.

Democratic lawmakers in Washington have demanded answers from the White House over the legality of the strikes, which United Nations experts have described as extrajudicial executions.

Asked about Petro's comments, the White House said Trump was "prepared to use every element of American power to stop drugs from flooding into our country and to bring those responsible to justice".

In the interview, conducted in New York where dignitaries from around the world have gathered for an annual high-profile United Nations meeting, Petro also accused the Trump administration of humiliating his people and said South American nations like his would not "bow down to the king".

After returning to office in January, Trump toughened his talk, as well as his trade policies, for all of Latin America as he began a major deportation sweep of people he says have illegally crossed the US southern border.

Trump also designated several drug-trafficking organisations and criminal groups in Mexico and elsewhere in Latin America as terrorist organisations.

As well as Tren de Aragua, Trump has taken aim at the Cartel of the Suns - a group that the US alleges is headed by Venezuelan leader Nicolás Maduro and other high-ranking Venezuelan officials, some drawn from the country's military or intelligence services.

The US military has moved to bolster its forces in the southern Caribbean over the last two months, including through the deployment of additional naval vessels and thousands of US Marines and sailors.

Petro has repeatedly sparred with his US counterpart. Pressed on whether he now risked further isolating his country, Petro said it was Trump who was isolating the United States with his foreign policies.

"Trump had already insulted me during a presidential campaign, he called me a terrorist," he said. (BBC)