A Tunisian charity launched an urgent appeal on Monday to help African migrants stranded in desert areas of the south after being driven out of the port city of Sfax.

Hundreds fled or were pushed to the harsh border area between Tunisia and Libya after racial tensions flared last week into violence against migrants from sub-Saharan African countries.

Dozens of other migrants were forced towards Tunisia's southern border with Algeria.

Beity, an non-governmental organisation helping victims of gender-based violence and discrimination, called on aid workers, charities and public institutions to "coordinate efforts and pool resources" for the stranded migrants.

"We have been witnessing for days... a real manhunt going on" in Sfax, Beity said in a statement, denouncing "security threats" to migrants and "their expulsion and deportation" towards the Sahara desert.

The crackdown on migrants in Sfax -- a departure point for many hoping to reach European soil -- erupted after the funeral of a 41-year-old Tunisian man who was stabbed to death on July 3 in an altercation between locals and migrants.

Tunisia has seen a rise in racially motivated attacks after President Kais Saied in February accused "hordes" of undocumented migrants of bringing violence, and alleging a "criminal plot" to change the country's demographic make-up.

Some 260 out of at least 450 migrants at the militarised buffer zone between Tunisia and Libya, near Ras Jedir, have been evacuated, media reports and rights groups said Monday.

They were taken to Tunisian cities including Medenine, Tataouine and Gabes. A dozen others were housed in the Tunisian town of Ben Guerdane, where an AFP correspondent saw some at a school building.

An official at Mali's embassy in Tunis told AFP "A dozen Malians who have fled Sfax in recent days, including one who broke his arm while trying to escape locals, have been taken into the embassy".

For those sent to near the Algerian border, the situation is becoming increasingly difficult, witnesses told AFP. "Please help us. If you can send the Red Cross here, help us, otherwise we will die," Mamadou, a migrant from Guinea who gave only his first name, told AFP by phone.

"There is nothing here. There's no food, there's no water." About 30 migrants have been abandoned to fend for themselves in a desert area near the Algerian village of Douar El Ma, close to the Tunisian border, he said.