The UN refugee agency Thursday voiced "concern" for the safety of 100 Arab citizens who went missing after seeking shelter in Algeria and others stranded at the border with Niger.
"Some 120 Syrian, Palestinian and Yemeni individuals were detained at the Tamanrasset Centre in southern Algeria before being taken to an area near the Guezzam border post (at the southern border with Niger) on 26 December," the UNHCR said in a statement.
Some members of the group were "known to UNHCR as registered refugees who have fled conflict and persecution or claim to have attempted to seek international protection in Algeria", it added.
The UN agency said 20 members of the group "remain stranded in the desert", several kilometres from the Guezzam border post.
"The other 100 individuals who were taken to the border are unaccounted for," it added.
Hacen Kacimi, an Algeria interior ministry official, told AFP on Thursday that a group of about 100 people, mostly Syrians from Aleppo, had been "expelled" on suspicion of links to jihadist groups.
Kacimi, who heads the ministry's migration department, said they had entered Algeria illegally and were put on trial in September and that the court ordered their expulsion.
His comments came after the Algerian League for the Defence of Human Rights on Monday denounced the deportation to Niger of 50 mostly Syrian migrants, including women and children, who were smuggled into the country in September.
Rights groups regularly criticise Algeria for its treatment of sub-Saharan migrants, many of whom are hoping to reach Europe.
An October report from the UN urged Algeria to stop collective expulsions of African migrants across its border with Niger, after rights groups accused Algiers or rounding up thousands of people and expelling them into the desert.
Algeria, which does not have asylum legislation, has faced an influx of sub-Saharan migrants in recent years, with rights groups estimating some 100,000 have entered the country in recent years.