A suspect has been arrested as a crackdown on a suspected terror group intensified, police confirmed on Sunday.

Riana Heymans, a member of the National Christian Resistance Movement (NCRM), has been in police custody along with two other people who are believed to have been harboring her, said Hawks, a special anti-crime unit affiliated with the South African Police Service.

The NCRM, also known as the Crusaders, is suspected of plotting to carry out attacks on national key points, shopping malls, and informal settlements across the country.

"She (Heymans) was arrested with two other people, whom we believe were harboring her in the Vaal area, Kilprivier (near Johannesburg), to be exact," spokesperson Hangwani Mulaudzi said.

Police have confiscated some firearms and documents which are subject for investigation, Mulaudzi said.

"We are hoping that we will be able to oppose bail," added Mulaudzi.

Heymans has been transported to Middelburg, Mpumalanga Province where she will be charged with NCRM self-proclaimed leader Harry Knoesen, said Mulaudzi.

Knoesen was arrested in Mpumalanga last week following a two-year investigation into an alleged terrorist plot by the movement.

Knoesen appeared in court in Mpumalanga on Friday on charges related to terror and the unlawful possession of a firearm and ammunition.