New Delhi, Nov. 2 -- The U.N. human rights chief said Friday that U.S. military strikes against boats in the Caribbean Sea and eastern Pacific Ocean allegedly carrying illegal drugs from South America are "unacceptable" and must stop.

The U.N. High Commissioner for Human Rights, Volker Turk, called for an investigation into the strikes, in what appeared to mark the first such condemnation of its kind from a United Nations organization.

Ravina Shamdasani, a spokeswoman for Turk's office, relayed his message Friday at a regular U.N. briefing: "These attacks and their mounting human cost are unacceptable. The U.S. must halt such attacks and take all measures necessary to prevent the extrajudicial killing of people aboard these boats."

She...