The FBI said it has rescued more than 50 children who were being victimized through prostitution in a national sting.

The operation, part of the Innocence Lost National Initiative, took place in 36 cities over the past 72 hours.

The FBI said 631 others, including 60 pimps, were arrested on local and state charges.

"Child prostitution continues to be a significant problem in our country, as evidenced by the number of children rescued through the continued efforts of our crimes against children task forces," Kevin Perkins, assistant director of the FBI's Criminal Investigative Division, said in a statement on Monday.

Local and state law enforcement agencies assisted the FBI in the 3-day operation.

"There is no work more important than protecting America's children and freeing them from the cycle of victimization," said Perkins. "Through our strategic partnerships with state and local law enforcement agencies, we are able to make a difference."

The Innocence Lost Task Forces and Working Groups have rescued nearly 900 children from the streets to date, the FBI reported.