Human trafficking is a modern form of slavery that must not be tolerated, a senior UN official and celebrities said.

Pop star Ricky Martin, Oscar-winning actress Emma Thompson and Egyptian first lady Suzanne Mubarak were among dignitaries on Wednesday who urged action at a three-day UN conference on trafficking.

"Two hundred years after the end of the trans-Atlantic slave trade, we have the obligation to fight a crime that has no place in the 21st century," said Antonio Maria Costa, head of the UN Office on Drugs and Crime.