Dozens of migrants from Niger heading for Algeria died of thirst in the Sahara desert after their vehicle broke down, local officials said Monday, while police said 19 survived.

"About 40 Nigeriens, including numerous children and women, who were attempting to emigrate to Algeria, died of thirst in mid-October," Rhissa Feltou, the mayor of the main northern town of Agadez, told AFP.

"Many others have been reported missing since their vehicle broke down in the desert," he said.

The army found the bodies of two women and three adolescents, a paramilitary policeman told AFP. No other bodies have so far turned up.

However, 19 survivors were taken to Arlit, the policeman said.

"Travellers told us that they saw and counted up to 35 bodies, mostly those of women and children, by the road," said Abdourahmane Maouli, the mayor of the northern uranium mining town of Arlit.

According to Feltou, two vehicles left Arlit with at least 60 passengers "around October 15", heading for Tamanrassett, an Algerian town in the heart of the Sahara.

When one vehicle broke down, the other drove on empty, leaving the passengers behind in a plan to find spare parts and bring them back for repairs, the mayor of Agadez said.

The migrants, short of water, dispersed in small groups in search of an oasis, Feltou said. After days of walking, five survivors reached Arlit and alerted the army, "who arrived too late at the scene."

A survivor told Niger's bimonthly Air Info that 82 people had perished, in a further conflicting report on the death toll.

Fatou N'Diaye of the International Organization for Migration in Niger said that 78 people were in the two vehicles heading for Algeria, and that 13 survivors had passed through the organisation's transit centre in Arlit.

"Like all the migrants we welcome, they were worn out and feeling very ill" upon arrival, she said.

In the lucrative business of transporting Africans fleeing conditions at home for what they hope will be a better life elsewhere, traffickers quite frequently abandon their human cargo in the desert, leaving them to near certain death.

Azaoua Mamane, who works for the non-governmental organisation Synergie in Arlit, said the group left behind consisted of "entire families, including very many children and women, who departed for Algeria, where they hoped to beg for their keep."

Niger is one of the world's poorest countries and has been hit by successive food crises.

The UN's Office for the Coordination of Humanitarian Affairs estimates that at least 30,000 economic migrants passed through Agadez between March and August of this year.

Libya, rather than Algeria, is more frequently the favoured country of transit for west Africans making the journey across the continent.

These migrants often look to Europe as their final destination, a security source told AFP, and use Libya as a jumping off point amid the relative chaos in the North African country since the fall of Moamer Kadhafi in 2011.

Humanitarian agencies say nearly 20,000 migrants have perished while trying to cross the Mediterranean Sea into Europe over the past 20 years.

The death of more than 300 Africans in a shipwreck off the Italian island of Lampedusa earlier this month has recently pushed the issue to the top of Europe's political agenda.