M23 rebels patrol near Rushuru in the Democratic Republic of Congo in this August 3, 2013, file photograph. Picture: James Akena/Files

Kinshasa - A crackdown on illegal immigrants in the Republic of the Congo has driven around 40 000 people from the neighbouring Democratic Republic of Congo back across the river border in a month, an official said Tuesday.

The Brazzaville authorities on April 3 launched an operation dubbed Mbata Ya Bakolo (“the slap of the elders” in the local Lingala language) to drive out illegal foreign workers.

The prime targets of the sweep have been citizens from the neighbouring DR Congo. Brazzaville and Kinshasa lie on either side of the Congo river, the only two capitals in the world in direct view of each other.

Kinshasa Governor Andre Kimbuta had said on Monday that the total number of returning immigrants neared 40 000.

An immigration official told AFP that about 30 000 people crossed the river from Brazzaville by Saturday and that around 3 000 had since done the same thing daily.

Voice for the Voiceless, a rights organisation based in Kinshasa, had last week accused the Brazzaville authorities of treating illegal workers in a “barbaric” way.

Among the thousands of people who washed up at Kinshasa's main port on Tuesday, many said they had not been expelled but were fleeing an increasingly hostile environment in Brazzaville.