Angolan authorities repatriated 640 Congolese nationals on Monday following a police crackdown on illegal migrants in Chissanda border post, Lunda Norte province in the northeastern part of the country, local police said in a statement.
Angola and the Democratic Republic of Congo share a 2,500-kilometre land border.
Lunda Norte province, 656km north of Angola's capital Luanda, shares a 770-kilometre border with the Democratic Republic of Congo.
According to police, the Congolese nationals tried to illegally cross the border post to reach the diamond exploitation zones.
Angola has extensive diamond reserves (estimated at 180 million carats), principally in the provinces of Lunda Norte and Lunda Sul in the northeastern parts of the country.