RABAT, Morocco — After landing at the Rabat airport in 2010, Zakaria Moumni, a former kickboxing world champion, was distressed when he was taken aside by security agents, arrested, blindfolded and taken on a ride under a blanket in the back seat of a car to a secret facility. He says he was held there for four days, during which he was deprived of food and water.

“There is no worse feeling than this hopelessness of being blindfolded and handcuffed naked without being able to control anything,” said Mr. Moumni, 34, who spoke from Paris, where he now lives. “They told me that I was in a slaughterhouse and that I was going to leave in small pieces.”

The facility where Mr. Moumni was taken, on Interior Ministry property in a forest in the city of Temara, a few miles south of Rabat, had been established years earlier as a black site for the Central Intelligence Agency to hold “enhanced interrogations” of terrorism suspects. But over the years after the Sept. 11, 2001 attacks, it proved to be a handy tool for the security forces of the Moroccan government as well.

The release of the United States Senate report on torture last month renewed debate about the merits of harsh interrogation techniques in fighting terrorism. But less attention has been paid to what human rights advocates call the damage the sites have done in their host countries, which they say have used them as a tool for terrorizing their political opponents.