South Africa's national police commissioner Fannie Masemola will testify Monday at a judicial inquiry investigating allegations of criminal infiltration in law enforcement, following testimony from a provincial commander who warned the justice system faces "total collapse."

Masemola takes the stand at the Madlanga Commission after three days of testimony from KwaZulu-Natal police commissioner Nhlanhla Mkhwanazi concluded Friday. The inquiry began Wednesday at Brigitte Mabandla Justice College in Pretoria.

Mkhwanazi implicated Police Minister Senzo Mchunu and former minister Bheki Cele in political interference. He alleged Mchunu disbanded KwaZulu-Natal's Political Killings Task Team without consultation after the unit uncovered links between organised crime and senior officials.

"The criminal justice system has been subject to continuous threat and sabotage," Mkhwanazi told the commission. "It is at real risk of total collapse if nothing is done."

The lieutenant general described investigations connecting weapons seized from businessmen to 18 murder cases. He said task team members received threats after uncovering connections between drug cartels and law enforcement officials.

Commission spokesperson Jeremy Michaels confirmed Masemola will testify Monday morning. Public attendance requires valid identification and weapons are prohibited at the venue.

President Cyril Ramaphosa established the commission in July after Mkhwanazi held a press conference making corruption allegations. The inquiry must submit an interim report within three months.

Retired Constitutional Court justice Mbuyiseli Madlanga chairs the commission. Chief evidence leader Terry Motau said individuals named in allegations will testify in later phases.

"If the allegations are proved true, that spells doom for South Africa's criminal justice system," Madlanga said in opening remarks Wednesday.

The commission has subpoena powers and can recommend institutional reforms. It cannot prosecute directly but may refer matters to prosecuting authorities.

Mkhwanazi testified that 121 case dockets were transferred from the disbanded task team to national headquarters without explanation. He said the decision to close the unit came via WhatsApp message from a civilian contact.