Black First Land First (BLF) has said that it will open cases against Eureka and Orania, calling them "apartheid enclaves".
This follows reports of the establishment of a new settlement that is only for white people.
The founder of the Eureka settlement, Adriaan Alettus Nieuwoud, is allegedly giving free land in the area to white people who wish to live there. Nieuwoud says he bought the land himself, using personal funds.
BLF has condemned Eureka and said it was "openly racist".
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The organisation also promised that it would be elected into government, after which it would pursue an "Anti-Racism Bill" in an effort to put a stop to settlements like Eureka.
"The so-called Eureka farm for whites only is not just illegal but shows how arrogant some whites have become," BLF said.
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