Apologies for the Wikipedia link, but unfortunately articles in English are quite lacking on this subject.

During the 1940s, the social democracy established more than a dozen of these camps and used them to contain left‐wing activists and certain foreigners. No deaths have been confirmed, but the camps may have held as many as three thousand inmates for most of the 1940s. The camps probably succeeded at terrorizing proletarians into submission, which would explain why the inmate count wasn’t higher.