Algerian authorities deported hundreds of West African migrants to Niger this week, trucking them thousands of miles across the desert in one of the biggest roundups seen this year, officials and rights activists said.

While Algeria has often sent migrants back to Niger since 2014 as the number of people risking their lives to Europe from West Africa through a dangerous route swelled, the latest group is different as it involved people from across the region, not just Niger, officials said, suggesting a more determined effort to remove immigrants.

By Friday, at least 1,000 migrants came in a convoy of about 50 trucks to Agadez in central Niger, a desert town where migrants from all over West Africa pay smugglers to take them on the treacherous journey north through the Sahara, an official in Agadez, the International Organisation for Migration (IOM) said.

Giuseppe Loprete, the head of IOM's mission in Niger put the figure at about 1,000 — 271 from Niger, the rest from West African countries, largely Mali and Guinea Conakry.

Algerian and Nigerien authorities were not immediately available for comment.

But Loprete told reporters that the IOM, which has a holding center in Agadez where migrants from across the region are housed and fed, is not directly involved in the latest deportation, as it was not contacted by Algerian or Nigerien authorities to help.

The migrants are instead being housed on the outskirts of town, said Isatou Abdou, who works for the U.N.’s human rights arm in Agadez, without confirming the numbers.

Reports indicated on Friday, more than 1,400 migrants have been forcibly deported from Algeria this month.

Many were rounded up in the capital Algiers and bused to Agadez, over 2,600 kilometers (1,600 miles) south.

Rights activists condemned the mass and summary deportation of migrants, including men and women who may have fled persecution or have worked for years in Algeria, as a violation of their rights.

Agencies