At least 180,000 Congolese citizens have crossed the border with Angola since 1 October most heading to the city of Kamako where they are living in precarious informal camps, local officials have confirmed.
The numbers are likely to be much higher as the Democratic Republic of Congo and Angola share more than 300km (186 miles) of border.
Many migrants are saying they were kicked out despite having documentation to live in Angola and there are unconfirmed reports that a number of them have been brutalized and even killed by Angolan forces.
The reason for the crackdown is unclear.
For many years, Congolese migrants have been in Angola, where they dig for diamonds on artisanal mines.
It could be linked to an attempt by the new Angolan government to take control over its mining industry.
