A dispute over the succession of the late South Africa's Zulu King, Goodwill Zwelithini, is now headed to court, local media report.

The first wife, Queen Sibongile Dlamini, is challenging the execution of the late monarch's will naming the next king - amid claims that his last will may have been forged.

The news of legal action comes days after the death of Queen Shiyiwe Mantfombi Dlamini Zulu.

She had been appointed as regent on 24 March after King Zwethilini died in hospital from diabetes-related complications at the age of 72.

But in the legal challenge that opposed Queen Mantfombi's appointment as regent, Queen Sibongile wanted the court to recognise her civil marriage to the late king as his only legally binding union. She also demanded 50% control of his estate.

On Sunday, the Zulu Prime Minister Prince Mangosuthu Buthelezi described the legal action as "shameful", while speaking to South Africa's public broadcaster SABC.

"Most of the members of the royal family are actually shocked by what she has done because she was still mourning. They, as the widows of the King in particular, and for them to rush to court in the manner they have done has actually disgraced the royal family," he told the broadcaster.