More than 400 people from across West Africa have been rescued from the desert in northern Niger in two days, the International Organisation for Migration said, in the latest recovery of migrants from the frontier region near Algeria.
Search and rescue teams found the migrants in two groups at the desert border town of Assamaka, IOM said, without specifying whether they had been pushed back across the border from Algeria - following previous claims by rights groups that migrants were dumped in the remote region.
Niger is a transit country for thousands of migrants heading to Libya and Algeria, key hubs for migrants trying to reach Europe.
The Saharan route is notorious for its dangers, which include breakdowns, lack of water and callous traffickers who abandon migrants in the desert.
Some 347 people from 13 countries, including Mali, Guinea and Senegal, were found in Assamaka on Monday after arriving on foot overnight, IOM said.
It added that most of them had been taken to a transit camp where they could receive food, water and medical assistance. A further 92 were rescued on Tuesday.
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The IOM has reported a sharp rise in the number of migrants left to walk across the border between Algeria and Niger through the desert this year.
In July, the UN body said it had rescued nearly 400 people "abandoned on the border with Niger and Algeria".
But Algeria lashed out at IOM, with Interior Minister Noureddine Bedoui denouncing "a campaign of non-constructive and unfounded criticism" against his government.
The European Union has been grappling with massive migration from Africa and the Middle East since 2015.
Niger has become one of the main crossing routes for poor migrants, with 90 percent of West African migrants passing through the country, according to the EU.
In 2015, Niger introduced a law making people-smuggling punishable by a jail term of up to 30 years.
The army also stepped up patrols in the desert.
In July, European Parliament President Antonio Tajani said the flow of migrants through Niger fell by 95 percent between 2016 and 2017.