Peter Nygard, the Canadian fashion executive, has been charged with sex trafficking, racketeering conspiracy and other crimes that involved dozens of women and teenage girls as victims in the United States, the Bahamas and Canada, federal prosecutors in Manhattan said on Tuesday.

Mr. Nygard, 79, used his company’s influence, its money and its employees to recruit adult and “minor-aged female victims” over a 25-year period for the sexual gratification of him and his associates, according to a nine-count federal indictment. He was arrested in Winnipeg, Manitoba, on Monday at the request of the United States under an extradition treaty, the U.S. attorney’s office in Manhattan said. He is now being held in a Manitoba jail.

The indictment accused Mr. Nygard of targeting victims from disadvantaged economic backgrounds and, in some cases, with a history of abuse. Mr. Nygard sexually assaulted some, it said, while his associates assaulted or drugged others “to ensure their compliance with Nygard’s sexual demands.”

Jay Prober, the fashion mogul’s lawyer in Winnipeg, denied the charges against his client, saying he expected Mr. Nygard to be vindicated. His lawyer in New York, Elkan Abramowitz, declined to comment.