Smugglers in Libya are auctioning migrants off as slaves, CNN has reported.

A team from the network witnessed a dozen men go under the hammer in the space of minutes at a property just outside Tripoli. Each was sold for $400.

One of the smugglers is heard offering "big strong boys for farm work."  

Another says: "Does anybody need a digger? This is a digger, a big strong man, he'll dig."

The journalists met two of the men who had been sold. They were so traumatised by what they'd been through that they could not speak, and they were so scared that they were suspicious of everyone they met.

Thousands of migrants pass through Libya every year, in an attempt to cross the Mediterranean and reach Europe. Once there, they are at the mercy of people smugglers, who they must rely on if they are to gain access to a boat making the crossing. 

But with the Libyan coast guard cracking down on smuggling trips, people smugglers are finding it harder to find a place to send migrants - and at times, it appears, auctioning them off to the highest bidder.