Dozens of migrants have died from dehydration from the Sahara Desert's scorching heat and thousands more remain stranded following a wave of deportations by Algeria.
Last year Algeria launched a crackdown on illegal immigration as well as stringent border controls across its southern frontier, with Algerian Foreign Minister Abdelkader Messahel labelling migrants as "a threat to national security".
In response to the crisis, the United Nations migration agency (IOM) said it is providing shelter for 3,500 expelled migrants in neighbouring Niger.
According to Giuseppe Loprete, IOM chief of mission in Niger, 1,500 arrived at the remote border village of Assamakka on a single day last month and IOM estimates state that at least 7,000 are expected to pass through in the year to June.
Migrants dropped there by Algerian authorities face a 250-mile journey to the nearest town. Many give up seeking transport and are forced to walk in extreme temperatures of up to 48 degrees Celsius.
"Most of them have no money or identity documents, food or water," Loprete said.
They are traumatised. In some cases they have been unable to get transport and have walked or they have been abandoned by human traffickers and don't know where they are.
"The territory makes it difficult to verify numbers but most groups we find have reported deaths along the way," Loprete said. "Recently we found a group that started out as 50 but only six remained alive. The total number of deaths must be in the dozens in this current crisis and definitely in the thousands since 2015."
The area has witnessed large migration flows as Niger's border with war-torn Libya is formally closed and heavily militarised, diverting the stream of migrants towards the Algerian border. Unofficial estimates put the total number of undocumented migrants in Algeria at 100,000.