FILE PHOTO: The Pentagon building is seen in Arlington, Virginia, U.S. October 9, 2020. REUTERS/Carlos Barria/File Photo

By Phil Stewart and Idrees Ali

WASHINGTON (Reuters) -The United States is sending the two survivors of a Thursday strike in the Caribbean to their home countries of Colombia and Ecuador to be detained and prosecuted, U.S. President Donald Trump said on Saturday.

The move, which was first reported by Reuters, means that the U.S. military will not have to grapple with thorny legal issues surrounding military detention for suspected drug traffickers, whose alleged crimes do not fall neatly under the laws of war, legal experts say.

"The two surviving terrorists are being returned to their Countries of origin, Ecuador and Colombia, for detention and prosecution," Trump said on Truth Social.

The U.S. military staged a helicopter rescue for the survivors on Thursday after the strike on their semi-submersible vessel, suspected of trafficking illegal narcotics. The strike killed the other two crew members on board.

The U.S. military flew the survivors to a U.S. Navy warship in the Caribbean after the rescue.

In his social media post, Trump said, "U.S. Intelligence confirmed this vessel was loaded up with mostly Fentanyl, and other illegal narcotics."

Trump did not provide any evidence, but did post a roughly 30 second video which appeared to show a semi-submersible vessel in the water before being hit by at least one projectile.

Speaking on Friday, Trump told reporters that the strike was against "a drug-carrying submarine built specifically for the transportation of massive amounts of drugs."

Colombia's president's office, Ecuador's communications office and the foreign ministries of both countries did not immediately respond to requests for comment.

The Trump administration has said the previous strikes killed 27 people, raising alarms among some legal experts and Democratic lawmakers, who question whether they adhere to the laws of war.

The strikes come against the backdrop of a U.S. military buildup in the Caribbean that includes guided missile destroyers, F-35 fighter jets, a nuclear submarine and around 6,500 troops as Trump escalates a standoff with the Venezuelan government.

On Wednesday, Trump disclosed he had authorized the Central Intelligence Agency to conduct covert operations inside Venezuela, adding to speculation in Caracas that the United States is attempting to topple Venezuelan President Nicolas Maduro.

Maduro has denied any connection to drug smuggling and denounced the U.S. boat strikes as a pretext for regime change, portraying them as violations of sovereignty and international law.

In a letter this week to the United Nations' 15-member Security Council, seen by Reuters, Venezuela's U.N. Ambassador Samuel Moncada asked for a U.N. determination that the U.S. strikes off its coast are illegal and to issue a statement backing Venezuela's sovereignty.

(Reporting by Phil Stewart and Idrees Ali. Additional reporting by Jeff Mason; editing by Diane Craft and Nick Zieminski)