NIAMEY (AFP) - The Niger government announced three days of national mourning for 92 migrants, nearly all of them women and children, who died in early October trying to cross the harsh Sahara desert.

In a statement published in the official Sahel daily on Friday, the government said it was "profoundly moved" by the tragedy and that the country would "pray for the memory" of the 52 children, 33 women and seven men who perished in the desert and whose decomposed bodies, some of them eaten by jackals, were found last week.

During the mourning period, which begins on Friday, flags will fly at half-mast across the territory of the deeply poor west African country in tribute to the victims, who all came from Niger, the statement said.

The tragedy occurred after two vehicles carrying would-be emigrants to Tamanrasset in the south of neighbouring Algeria both broke down. The victims are believed to have died of thirst.

The security source said that 21 people out of 113 managed to survive. Two of them arrived in the north Nigerien uranium-mining town of Arlit and 19 reached Tamanrasset, but were sent back to Niger.

A woman who came from south Niger and allegedly organised the journey was detained by security forces in Tamanrasset, where she lived, and sent back to Arlit, where she was locked up, the security source said.

Niger is one of the world's poorest countries and regularly faces food crises, leading many to try and flee the country abroad.

Migrants are often found dead in the north African desert, frequently abandoned by people smugglers to their fate, but not usually on the scale of the latest tragedy.