The extensive, three-day sweep took place in 76 US cities in conjunction with local, state, and federal law enforcement, as well as the the National Center for Missing and Exploited Children (NCMEC), it said in a statement.

Most of the freed youths are young teenagers aged 13 to 16, said Ronald Hosko, assistant director of the FBI's Criminal Investigative Division. "Our goal is that child trafficking is openly discussed," he told reporters.