The United States military has confirmed that at least 157 people have been killed in lethal strikes against alleged drug-trafficking boats off Latin America, described as a campaign of extrajudicial killings by legal experts.

Senior defence official Joseph Humire said that 47 “narco-trafficking vessels” have been struck in the Caribbean and Eastern Pacific since the campaign began in September, in a written statement to members of the US Congress.

Asked by lawmakers on Tuesday whether the quantity of drugs entering the US has gone down, Humire stated that the movement of drug-trafficking vessels had decreased by 20 percent in the Caribbean.

“We’ve measured the decrease in the movement of the vessels,” said Humire.

“But that’s a no in terms of the drugs actually getting into the US,” Representative Adam Smith responded.

Experts have expressed scepticism that the strikes are having any significant impact on the drug trade, and legal scholars have said that the campaign is a clear violation of international law and is blurring the distinction between armed conflict and criminal activity. Under international law, military force is permitted for the former, but not the latter.

The Inter-American Commission on Human Rights (IACHR) is holding hearings on the strikes, and advocates hope that the hearings could open the door to possible legal accountability for those responsible. (Al Jazeera)