Algeria is accused of leaving 4,000 migrants in the desert to walk 15 kilometres to the border with Niger.
A new Doctors Without Borders (MSF) report found that over the past four months the migrants were left without food, water or direction, despite the global pandemic.
The international medical aid group said the process broke international human rights legislation.
Among the 4,370 cases documented by MSF since January of this year were pregnant women, an individual wounded by gunfire and another with a broken leg.
Nearly all had made their way to Algeria from West Africa or South Asia.
With many fleeing the chaos that dominates much of West Africa, and keen to avoid the instability and exploitation of Libya, Algeria at least offers some kind of life, as well as the potential for onward travel to Europe.
Between 2019 and 2020, MSF estimated that 53,000 migrants made their way to Niger's border with Algeria. In the first four months of this year, a further 5,000 arrived.
Many get a glimpse of a new life once they enter Algeria, before being arrested, held – often without food – and deposited in the desert at a location that has come to be known as Point Zero, MSF said in the report released in mid April.
From there, they must walk the 15 kilometres to the village of Assamaka, in Niger.
Even in the height of summer, Algerian lorries and buses left depositing migrants, including the young, the old, the infirm and pregnant women in the desert, before leaving them to endure temperatures of anywhere up to 48°C as they make their way across the desert sands.
Others are dumped at night and left to navigate through the desert in darkness. Some never make it, although the death toll is unknown.
Safi Keita from Mali was four months pregnant when she was arrested in Algeria in November 2020. She had left her two other children with her mother back home, before establishing herself as a spice seller in Algeria.
“The gendarmes broke down the door,” Ms Keita told MSF. “They took everything: money and phones. Then they took me to the police station.”
From the police station, Ms Keita was transferred to a detention centre, where she was held for four days in what she alleges were unsanitary conditions with only bread to eat.
Despite the pandemic, nobody was wearing a mask.
“Although I was pregnant, I received no special treatment,” she said. “The guards had no compassion towards me or my physical condition.”
Ms Keita's story is echoed by dozens of others interviewed by MSF as they monitor Niger's border.
Many of those who arrive at Assamaka allege Algerian security forces beat and robbed them.
Traore Ya Madou from Mali had worked in Algeria for seven years by the time he was arrested and taken to a police station late last year.
“They searched us and took off our underwear – it was inhuman treatment. I had €2,500 ($3,011) on me and the officers took everything. They beat me so savagely that I had to go to hospital,” he told the NGO.
The hundreds of migrant testimonies collected by MSF suggest violence, including psychological abuse, is widespread.
"Violence is always underreported," Nour El Houdi Nafti, sub-Sahara regional representative for MSF told The National.
"We talk to all the migrants when they arrive, but many aren't ready to open up. I can't say how many may have been beaten, but all have suffered harm."
Europe has taken strict measures to try to stop such migration from North Africa.
In Valletta, Malta in 2015, legislators codified their position, with European and African countries all agreeing to strengthen border controls and facilitate the return – voluntary or otherwise – of anyone found to have entered the country illegally.
But observers suggest Algeria's wholesale interpretation of that agreement is running counter to its wider obligations under international and human rights laws.
"All we're asking is that Algeria respects international law, and those governing refugees in how they deal with migrants," Ms Nafti said.
"There has to be respect and dignity for the individual and each individual's case needs to be heard."
For the EU at least, Algeria provides a sturdy bulwark against the spectre of uncontrolled migration, its vital role highlighted by the relative collapse in Libya's border security.
While the tough stance may be popular with proponents in Brussels, analyst Zine Labadine Ghebouli from the Washington Institute suggested one of the main motivations for Algiers' unflinching approach is fear of the religiously driven unrest hat permeates West Africa.
"Algeria is still scarred by the 90s … After the war on Islamist terrorism, the idea of allowing access to anyone from the sub-Sahara became unthinkable," he said.
"The risk to the country's stability might be incredibly slight, but this is really about Islamist infiltration, which taps into a very painful public fear," Mr Ghebouli said.
