GENEVA/ALGIERS - The United Nations on Tuesday urged Algeria to stop rounding up and expelling sub-Saharan migrants, highlighting an influx of immigrants from Mali and Niger that Algeria says it needs UN help to address.Hassen Kacimi, a senior official at Algeria's Interior Ministry, told Reuters on Saturday that Algeria had called for help from the international community, while the United Nations had done little to save the migrants.UN spokeswoman Ravina Shamdasani told a regular UN briefing in Geneva that deportations and expulsions have increased markedly since the second half of 2017, and a UN human rights team went to Niger to investigate this month."What they heard was that Algerian authorities frequently carry out mass round-ups of sub-Saharan African migrants in various parts of the country," Shamdasani said.Of 25 migrants interviewed by the UN team, only one had had her passport checked before being expelled. Most had been told to put thumbprints on Arabic documents they could not read.Most were not told why they were being detained and were not allowed to pick up their belongings, passports or money before being expelled. Some were taken straight to Niger, others were held in military bases, in inhuman and degrading conditions, before being taken south."[Some] are crammed into big trucks to be transferred to the Nigerien border where they are abandoned and left to walk hours in the desert heat to cross the border into Niger," she said.Algeria says it faces a huge influx of migrants.