The US military says it struck two boats on Wednesday that it said were carrying drugs, killing five people on board.
The U.S. Southern Command did not say where it carried out the latest strikes, but U.S. forces have been targeting suspected narco-trafficking ships across the Caribbean and eastern Pacific for three months.
Wednesday's strike came a day after the United States targeted what it said were "three narcotics trafficking vessels traveling in convoy," killing at least three people.
The Trump administration has framed its operations as a non-international armed conflict with the suspected traffickers, but legal experts say they could violate laws governing such conflict.
In total, more than 30 strikes against ships have taken place as part of the Trump administration's "war on drugs," killing more than 110 people since the United States carried out its first attack on a ship in international waters on September 2.
That first attack has drawn close attention from lawmakers in Washington since it emerged that U.S. forces struck the targeted boat twice.
Two people who had survived the first impact and were clinging to the hull of their boat were killed in the second.
Some lawmakers have expressed concern that the "double tap" strike violates the rules of engagement.
In its message announcing the December 30 three-ship convoy strike, US Southern Command said there were a number of survivors, without specifying how many.
It said "the remaining narcoterrorists abandoned the other two ships, jumping overboard and distancing themselves before subsequent fighting sank their respective ships."
He said the U.S. Coast Guard was "immediately informed" to search for survivors.
The Reuters news agency reports that a U.S. official who asked not to be named said eight survivors were being sought.
It is not yet known whether any of them have been found.
The United States has provided no evidence that the vessels it targeted were carrying drugs, but in its most recent message, Southern Command still insisted that "intelligence confirmed that the vessels were transiting known drug trafficking routes and engaged in narcotics trafficking."
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