Although Niger recently passed new tougher laws against slavery, more than 870,000 people - about seven percent of the country's population - still live in conditions of forced labour, according to Timidria, a local human rights group.
The organisation, whose name means "Brotherhood" in the Tuareg language, recently announced the results of a survey conducted in August last year in six of Niger's eights administrative regions. This showed that 870,364 people still worked in servitude. The vast majority - 602,000 - were in the southwestern Tillaberry region, where the capital Niamey is situated.
Slavery is a long ingrained tradition in this poor landlocked country of 11 million people on the southern edge of the Sahara, which achieved independence from France in 1960.
Timidria said the custom was especially prevalant amongst nomadic pastoralists of the Tuareg tribe.
Its survey found that, apart from Tillaberry, the main concentrations of slaves were in Agadez region in the desert north, where 87,000 people were living conditions of forced labour, and in Tahoua region, adjacent to Tillaberry in the southwest, where it found 59,000 slaves.
Over the years, numerous workshops and symposiums have been held to expose the continuation of slavery in Niger. Parliament recently passed a law which recognises "slavery and slave-like practices" as crimes punishable with a prison sentence of up to 30 years.
The International Labour Organization defines as "forced labour" any activity which an individual is forced to perform services under threat of punishment without his or her own consent. This international definition excludes national military service, communal service or work imposed to an individual sentenced to communal service.
In Africa, Niger, Mauritania and Sudan are considered the main countries were slavery persists.
Many slave-owners interviewed by Timidria said the forced labourers were an inheritance and a responsibility.
"We inherited these slaves from our parents, but I did not know it was slavery", the organisation quoted one Tuareg chief as saying. "They are victims who don't want to leave us".
According to university professor, El Back Adam, Niger's slaves refuse to leave their masters despite the terrible conditions in which they live, because at least "they have a roof under their head and something to eat."