South Africa's National Assembly speaker announced on Thursday that she would take "special leave" following investigators raiding her home as part of a graft probe and calls for her resignation.

Coming just over two months before national elections, the raid adds to the woes of the ruling African National Congress (ANC), which is struggling in the polls amid accusations of graft and mismanagement.

"Given the seriousness of the allegations and the attendant extensive media speculation, I have decided to take special leave... effective immediately," speaker Nosiviwe Mapisa-Nqakula said in a statement.

Investigators raided her house on Tuesday as part of a corruption probe, which she has vowed her full cooperation.

South African Defence Minister Nosiviwe Mapisa-Nqakula (L) attends the commemoration ceremony in Pretoria during the first anniversary of former President and Nobel peace laureate Nelson Mandela's death on December 5, 2014.

Mapisa-Nqakula is accused of soliciting 2.3 million rand ($121,000) in bribes from a former military contractor when she served as defence minister between 2014 and 2021 before being appointed as speaker.

South Africa's leading opposition party, the Democratic Alliance (DA), on Tuesday called for her to step down.

"The ANC will enforce its integrity and step aside policies based on the facts as they arise," the ruling party said in a statement.

The "step aside" rule is an internal party policy that requires members to voluntarily step down from duties when charged with corruption.

The country heads to polls on May 29.

In power since the advent of democracy in 1994, the ANC is expected to see its share of the vote drop below 50 percent for the first time.

This might force it to form a coalition to remain in power.

Mapisa-Nqakula has denied any wrongdoing.

"The decision... is meant to protect the integrity of Parliament and ensure its sacred duty and its name continue unblemished," Mapisa-Nqakula said.