Washington DC - The US likely played a role in violent attacks on three fishing vessels off Ecuador's coast earlier this year, which left at least eight people missing, Human Rights Watch (HRW) reported on Tuesday.

The attacks allegedly occurred between January and March, as the US military ramped up its controversial strikes against unidentified boats it claims are transporting drugs near Latin America.

At least 215 people have been killed in the strikes, which rights groups, including HRW, have condemned as extrajudicial killings because they have targeted civilians who pose no immediate threat to the US.

"Between January and March, the fishing vessels La Negra Francisca Duarte II and the Don Maca came under attack in the Eastern Pacific. A third vessel, the Fiorella, disappeared on January 20 with eight of its crew members," HRW said in a new investigative report.

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"The US Department of Defense and Coast Guard have denied responsibility for the attacks," HRW said.

The nonprofit group's investigation – which involved interviews 13 survivors of the attacks – concluded, however, that the US "had some level of involvement in, or knowledge of, these attacks."

"On March 17 and 26, crew members of La Negra Francisca Duarte II and the Don Maca, respectively, said they were attacked by armed drones," the report said.

"Survivors said that armed US nationals wearing military-style uniforms bearing US flag insignias detained them aboard a nearby blue-and-white vessel, and then transferred them to the Salvadoran Coast Guard," it continued.

HRW also condemned the US-Ecuador joint military action against criminal drug trafficking, alleging the use of torture and arbitrary detentions.

"The US Congress should demand clear answers from the Trump administration to the many questions surrounding its security cooperation with Ecuador," the report concludes.