Former Malaysian leader Mahathir Mohamad, joining anti-government protesters for a second day on Sunday, called for a "people's power" movement to topple Prime Minister Najib Razak over a financial scandal.

"The only way for the people to get back to the old system is for them to remove this prime minister," said Mahathir, a deeply respected 90-year-old who was once Najib's patron and is now his fiercest critic.