The voice over the phone is insistent: “Someone needs to come now! We are going to die. It is 40 degrees, and we don’t have a drop of water."

Kelvin is an undocumented Nigerian. He says authorities detained him in Sfax, in the central-eastern part of Tunisia, before forcing him to board a bus chartered by the Tunisian authorities and leaving him in the desert with “at least 150 people”.

The videos Kelvin sent show women and even babies in the middle of the desert, where the heat is intense under a blazing sun. GPS coordinates sent by the migrant show the group is near the militarized zone of Ras Jedir on the Libyan border. 

“There are pregnant women, along with a few children,” said the Nigerian, who still does not understand what happened. “We are here, maybe in Libya, I don’t know. Libyan guards came [Tuesday] in the afternoon, they counted us, they gave us a little water and biscuits before leaving.”

The few, small bottles were emptied in a few minutes. Since then, Kelvin has not had anything to drink. One night went by and the group was still waiting for help. “We are going to die of thirst. It is too hot to stand. Why aren’t the NGOs [non-governmental organizations] here?”

‘The Tunisian Red Cross cannot resupply them’

The coordination charity Alarm Phone, which helps migrants in distress, was able to localize Kelvin’s group and alert NGOs present in the buffer zone. Yet none of them were able to contact Kelvin, who is on the Libyan side of the border.

“We think there are several small groups divided in the same zone in the desert,” explained one of the collective’s members. “The Tunisian Red Cross cannot resupply them [with food and water]; they aren’t authorized to access the Libyan territory.”

Migrants and associations have already accused Tunisian authorities of arresting African migrants in Sfax and the surrounding cities and later abandoning them in the desert without any resources. Tunisian authorities have driven several hundreds of migrants to Ras Jedir, at the Tunisian-Libyan border, last week. Following a backlash in the media and videos shared on social networks, Tunisian authorities relocated the migrants to shelters in Médenine, Tataouine and Ben Guerdane. 

According to Kelvin, the Tunisian authorities are trying to leave the detained migrants further than ever, in zones inaccessible to the media and NGOs. 

In another video Kelvin sent Wednesday morning, another man in the group -- a Sierra Leonean -- begs for help. Hiding from the sun, on his knees, he asks for assistance. “We are suffering. We haven’t had anything to eat since yesterday,” he said, covering his face with his hands. “We are going to die here. Help us.”

 ‘Our cell phones will be off soon, we are going to be alone’

To their utter despair, Kelvin and his group will soon be no longer able to communicate with NGOs by phone. The batteries on their cell phones are almost out. Alarm Phone has already lost contact with the migrants abandoned on the Algerian side of the desert. Their phones have probably already run out of battery. A race against the clock is playing out in the desert. “We only have two cellular phones among us”, Kelvin explained. “They will be turned off soon, and we will be alone, without any options.”

Read more: Tunisia: Deaths at the border

According to Alarm Phone, around 600 migrants are in the Libyan desert, while Human Rights Watch says at least 150-200 migrants are somewhere in the Algerian desert, without water or food. “It is the urgency of the moment," said Salsabil Chellali, of HRW. “These people are risking their lives if they aren’t saved immediately.”

Two bodies have already been found in the Algerian desert. Around 10 days ago, one body was found in the Hazoua desert, near Algeria's border, and another was discovered on Monday night, said Nizar Skander, a spokesman for the court in the southeastern Tozeur district. 

The expulsions of sub-Saharan African migrants have been on the rise since the xenophobic speech of Tunisian President Kais Saied last February, but they have intensified following the killing of a Tunisian man on June 3 in an altercation between locals and migrants. Authorities have recently expelled dozens of African migrants from Sfax, a departure point for many migrants hoping to reach Europe. Hundreds of Tunisian protesters even protested in Sfax in June to denounce the presence of undocumented sub-Saharan migrants in the city.

“Tunisia has given a lesson to the world with the way it has taken care of its migrants," the Tunisian president said on Monday, adding that the country nevertheless “refuses to be a substitute homeland and will only accept those who are regularized.” He did not say anything about the migrants abandoned in the desert. 

Read more: Why is the Tunisian president going after sub-Saharan migrants?