Story highlights The operation took place over the last week in more than 100 cities, FBI says

It involved nearly 400 law enforcement agencies

FBI director: "Our children are not for sale"

The FBI has rescued 168 children and arrested 281 pimps in a countrywide crackdown on child sex trafficking.

The operation, which took place over the last week in more than 100 cities, involved nearly 400 law enforcement agencies, authorities said Monday.

The message, said FBI Director James Comey, should be clear: "Our children are not for sale. ... We will respond and crush these pimps who would crush these children."

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Since 2008, the FBI and its partners have rescued close to 3,600 children. The agency said investigations have led to 1,450 convictions and the seizure of more than $3 million in assets.

"These are not far-away kids in faraway lands. These are our kids, on our street corners, our truck stops, our motels, our casinos. These are America's children," Comey said.

Speaking alongside the director, Leslie Caldwell, assistant attorney general for the Justice Department's criminal division, stressed scores of more children remain victimized.

She urged anyone with information about such abuse to contact authorities.

"Just one call, just one online report could mean all the difference for a child who now can only dream of a normal childhood and a life outside prostitution," Caldwell said.