South African police are securing roads around parliament ahead of expected protests against President Jacob Zuma, who will give a state-of-the-nation address amid harsh criticism of his conduct.

Zuma could face disruption inside the parliament building during the Thursday evening speech, which will be shown live on television. Some opposition lawmakers have threatened to interrupt proceedings because of a scandal over millions of dollars in state spending on the president's private home.

Zuma offered to pay back some money in a concession to critics, who accuse him of violating the constitution.

The president is also under pressure to explain why he fired Finance Minister Nhlanhla Nene in December, a move that unsettled investors and further weakened the national currency.

South Africa is struggling with slow economic growth.