The bodies of 87 migrants were found in Niger's desert north after they died of thirst just a few kilometres from the border of Algeria, their planned destination, sources said.
The corpses of the seven men, 32 women and 48 children were in addition to five bodies of women and girls found earlier, a security source said yesterday.
All died in early October after a failed attempt to reach Algeria that began in late September, the source added.
Almoustapha Alhacen, from local aid organisation Aghir In'man, confirmed the death toll and gave a graphic account of discovering the bodies.
"The corpses were decomposed; it was horrible," he said.
"We found them in different locations in a 20-kilometre (12-mile) radius and in small groups, often under trees, or under the sun. Sometimes a mother and children, but some lone children too," Alhacen said.
Nigerien officials said on Monday that dozens of migrants, most of them women and children, had died of thirst in the Sahara desert earlier this month.
Rhissa Feltou, the mayor of the main northern town of Agadez, told AFP that two vehicles were carrying the migrants when one broke down, and they were all left behind in the desert while the remaining vehicle was driven off.
However, 21 people had survived, the security source said, including a man who walked 83 kilometres to the city of Arlit, northern Niger, and a woman who was saved by a driver who came across her in the desert and took her to the same city.
Nineteen others reached the Algerian city of Tamanrasset but were sent back to Niger, the source added. Niger is one of the world's poorest countries and has been hit by successive food crises.
Libya, rather than Algeria, is more frequently the favoured country of transit for west Africans making the journey across the continent, many of whom aim to travel on to Europe.
The UN's Office for the Coordination of Humanitarian Affairs estimates that at least 30,000 economic migrants passed through Agadez, northern Niger's largest city, between March and August of this year.