Opposition lawmakers have interrupted South African President Jacob Zuma during an annual address to parliament, saying he should answer questions about a scandal over more than $20 million in state spending on his private home.

Zuma began his state-of-the-nation speech Thursday evening, but several opposition lawmakers rose to their feet to protest the president's purported failure to provide answers about the spending at his Nkandla residence.

Julius Malema, leader of the opposition Economic Freedom Fighters, says Zuma should refund the money to the state.

Zuma has denied any wrongdoing, saying government security officials controlled the spending project.

Earlier, the start of Zuma's speech was delayed because of opposition allegations that the cell phone signal in the parliament had been jammed. The signal was later restored.