The bodies of 87 migrants were found in Niger's northern desert after they died of thirst just a few kilometres from the border of Algeria, their planned destination, security officials 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.
All died in early October after a failed attempt to reach Algeria that began in late September, the source added.
Almoustapha Alhacen, a spokesman of 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 20km radius and in small groups, often under trees, or under the sun. Sometimes a mother and children, but some lone children too," Alhacen said.
The bodies were buried according to Muslim rites, "as and when they were found," added Alhacen.
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. Two vehicles carrying the migrants broke down, one about 83km from the city of Arlit in northern Niger where they had set off from, and another at 158km, a security source said.
"The first vehicle broke down. The second returned to Arlit to get a spare part after getting all the migrants it was carrying to alight, but it too broke down," said the source.
"We think that the migrants were in the desert for seven days and on the fifth day, they began to leave the broken down vehicle in search of a well," said the source.
However, 21 people had survived, the source said, including a man who walked to Arlit 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.