NOUAKCHOTT - Born a slave, like his entire family, Matalla Mbreik toiled from dawn to dusk selling water and tending his master's flocks on the lonely fringes of the Saharan desert, until he could take no more.

"I still have the scars from my beatings, like my mother and sisters," said the 32-year-old Mauritanian, staring at the floor, dressed in flowing pale-blue embroidered robes."All they gave us to eat were leftovers."

After years spent dreaming of escape, Mbreik seized his chance two months ago when a Mauritanian army truck passed him searching for an oasis in the desert.

"I told them to shoot me rather than take me back to my master," said Mbreik, red-faced with shame, sitting in the office of anti-slavery group SOS-Slave.

Although banned by law in 1980, slavery in Mauritania has persisted, perpetuated by poverty and rigid customs. Authorities long denied its existence but campaigners estimate there are still hundreds of thousands of slaves among the 3 million population -- the highest ratio in the world.