The UN's human rights chief has condemned US military strikes on vessels allegedly carrying drugs in the Caribbean and Pacific, saying the lethal attacks violate international law and amount to extrajudicial killing.

Volker Türk said on Friday that more than 60 people have reportedly been killed in US strikes since early September.

Calling the attacks unacceptable, he said Washington must halt them immediately and conduct prompt, independent and transparent investigations.

President Donald Trump has said the strikes are necessary to stem the flow of drugs into the US and he has the legal authority to continue bombing boats in international waters.

Secretary of Defence Pete Hegseth has stated that strikes target vessels operated by drug-trafficking groups designated as terrorist organisations by the US, asserting that the Western Hemisphere is no longer a safe haven for narco-terrorists bringing drugs to our shores to poison Americans.

Türk, while acknowledging the challenges of tackling drug trafficking, said in a statement that the circumstances for the deadly strikes find no justification in international law.

He emphasized that combating drug trafficking is fundamentally a law-enforcement issue, governed by strict limitations on the use of lethal force as outlined in international human rights law.

According to him, the intentional use of lethal force is only permissible as a last resort against individuals who pose an imminent threat to life. However, based on publicly available information, it appears that none of the targeted individuals on the boats posed such a threat.

He urged the US to employ law enforcement methods like intercepting boats, detaining suspects, and prosecuting individuals if necessary.

Most strikes have largely occurred off South America's coast in the Caribbean, with recent attacks in the Pacific reportedly resulting in at least 18 deaths.

Given the escalating situation, US deployments in the region include troops, aircraft, and the USS Gerald R Ford warship.

The strikes have been met with condemnation from leaders in the region, alongside concerns from both Democrats and Republicans in the US Congress regarding the president’s authority to escalate military actions.

Mexican President Claudia Sheinbaum has stated her government’s disapproval of the attacks, insisting on adherence to international treaties.

The situation has raised tensions between the US and regional governments, significantly Colombia and Venezuela, with the US imposing sanctions on Colombian president Gustavo Petro over perceived failures in combating drug trafficking.

Petro asserts that his administration has been actively fighting against drug trade for many years.

Trump has accused Venezuelan President Nicolas Maduro of leading a drug-trafficking organization, a claim Maduro denies. Venezuelan officials have suggested that US actions might be aimed at seizing the country’s natural resources.