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In recent years, people around the world have lost hundreds of millions of dollars to online romance scams.

One of the most lucrative of these, being run by criminal gangs across South East Asia, is called the “pig butchering romance scam”.

The scammers refer to their victims as pigs, whom they fatten up to be “butchered” – or conned, out of as much money as possible.

A BBC World Service investigation has spoken to former insiders, who reveal the brutal conditions facing many of those working as scammers and the sophisticated techniques that are used.

Watch the full documentary on the BBC iPlayer, and read our previous coverage on the issue here.