The Pentagon's independent watchdog is probing the legality of the US military's widely criticised operation targeting boats on allegations of drug trafficking, that has killed at least 192 people, US media reported on Monday.
President Donald Trump's administration began striking vessels in the Caribbean and eastern Pacific Ocean in September last year, insisting it is effectively at war with what it calls "narco-terrorists" operating out of Latin America.
But legal experts and rights groups suggest the attacks could amount to extrajudicial killings because they have apparently targeted civilians who do not pose an immediate threat to the United States.
Trump's administration has also not provided definitive evidence that the vessels it has attacked as part of Operation Southern Spear are involved in drug trafficking.
The backlash from the operation is a blow to US Secretary of Defense Pete Hegseth, who has said that the campaign to hunt down boats allegedly bringing drugs from South America has been so successful that it is now hard to find targets.
"The scope of this evaluation includes the joint process for targeted vessels in the US Southern Command area of responsibility as part of Operation Southern Spear," the Pentagon's independent inspector general's office said in a statement quoted by Bloomberg.
The probe aims to determine whether the Pentagon followed the Joint Targeting Cycle -- which provides six key steps for carrying out a military operation -- when conducting the strikes, the agency said in a memorandum from May 11.
"We will perform the evaluation at the Pentagon and USSOUTHCOM headquarters" in Florida, it added.
The deadly strikes have marked a stark shift in the US approach to drug trafficking, which has historically focused on interdicting vessels and seizing the material.