Algeria has banned all Syrians from entering the country via its southern borders, hours after a rights group reported that 50 Syrians and Palestinians had been deported to neighbouring Niger in the last week.

Hassen Kacimi, the head of migrants policy at the interior ministry, said that Syrians seeking refuge this way were suspected to be armed fighters.

"We have hosted 50,000 Syrians in the past few years for humanitarian reasons," Kacimi told Reuters news agency, alluding to refugees from Syria's civil war.

"But we cannot accept members of armed groups fleeing from Syria when it comes to our security."

Algeria went through years of devastating civil war with armed groups in the 1990s. While violence is now greatly diminished, sporadic attacks continue in isolated areas.

Kacimi said around 100 people had reached the southern border with the help of local armed escorts in recent weeks but were intercepted and expelled shortly after they slipped into Algeria.

He said that the Syrians had transited Turkey, Jordan, Egypt, Sudan and Niger or Mali using fake Sudanese passports.

"This is a criminal network and we must be very vigilant not to allow them to get into Algeria," he added.

Earlier on Wednesday, a local human rights group said Algerian authorities had deported 50 Palestinians and Syrians on December 25 and 26.

According to La Ligue Algerienne pour la Defense des Droits de l'Homme (LADDH), the majority of the refugees were Syrian nationals and were transferred via buses to Niger.

Algeria's south and southeast are largely empty desert regions but it has beefed up its security there after neighbouring Libya and northern Mali and Niger fell into the hands of various armed factions.

Since its 1990s' civil war, Algeria has become an important ally against armed groups active in the arid Sahel region of North and West Africa.