Seventy-nine teenagers have been rescued as part of a three-day sweep of sex-trafficking rings in the US.

The FBI said 104 alleged pimps were arrested during the sting operations in 57 US cities including Atlanta, Sacramento and Ohio.

The crackdown is part of a broader inititive launched in 2003 called Operation Cross Country to combat child-sex trafficking.

The teenagers, aged from 13 to 17 years old, were all US citizens. They included 77 girls and two boys, who will now be placed with child welfare organisations.