The United States began carrying out the strikes -- which experts say amount to extrajudicial killings even if they target known traffickers -- in early September, and has now destroyed at least 14 vessels in the Caribbean and Pacific.

In three strikes carried out Monday in international waters, 14 "narco-terrorists" were killed and one survived, Hegseth said in a post on X -- making it the deadliest day of the US campaign so far.

"The four vessels were known by our intelligence apparatus, transiting along known narco-trafficking routes, and carrying narcotics," he said.

"We will track them, we will network them, and then, we will hunt and kill them," Hegseth said of drug traffickers.

But Washington has yet to make public any evidence that its targets were smuggling narcotics or posed a threat to the United States.

The Pentagon chief's post included video of the strikes, the first of which targeted two stationary boats that appeared to be moored together, while the others hit vessels that were speeding across open water.

Hegseth said that US Southern Command (SOUTHCOM) immediately started searching for the sole survivor of the strikes, and that Mexican authorities "accepted the case and assumed responsibility for coordinating the rescue."

- Galapagos base? -

He did not specify what happened to the survivor or if the person was found, and SOUTHCOM referred a question on the survivor to Mexico.

Mexico's Navy said it was searching some 400 nautical miles (740 kilometers) southwest of the port of Acapulco.

The announced drug interdiction operation has seen a major US military buildup around Latin America.

The US has deployed seven US Navy warships as well as F-35 stealth warplanes, and ordered the USS Gerald R. Ford aircraft carrier strike group to the region, bringing a massive increase in firepower.

The unusually large US military presence in the Caribbean is coming face to face with Hurricane Melissa, requiring some assets to be moved to safety.

Washington has also carried out multiple shows of force with B-52 and B-1B bombers flying near Venezuela's coast, the most recent of which took place on Monday.

Regional tensions have flared as a result of the strikes and the military buildup, with Venezuela saying the United States is plotting to overthrow President Nicolas Maduro, who has accused Washington of "fabricating a war."

Ecuadoran President Daniel Noboa, a staunch US ally, meanwhile said Tuesday that his country could host a foreign military base in the famed Galapagos Islands that could be used to combat drug and fuel trafficking, as well as illegal fishing.

Noboa did not specify which country could establish the base in Ecuador, a major hub for cocaine trafficking, but has talked of "various countries," including the United States.