Tens of thousands of Malaysians are protesting in the capital Kuala Lumpur and elsewhere, calling for Prime Minister Najib Razak to step down over a financial scandal.
Protesters are angered by a $700m (£455m) payment made to his bank account from unnamed foreign donors.
It was discovered last month during a probe into alleged mismanagement at the debt-laden state fund 1Malaysia Development Berhad (1MDB).
Mr Najib has denied any wrongdoing.
Saturday’s rally is expected to continue into Sunday. The pro-democracy group Bersih has also called for protests in the cities of Kota Kinabalu and Kuching on the Malaysian side of Borneo.
Kuala Lumpur authorities have rejected the group’s application for a permit to protest and Malaysian police have declared the rallies illegal.
Security is tight: access to Kuala Lumpur’s Independence Square has been blocked. Eyes will be focused on any possible army intervention.
At the last big rally in 2012, police used water cannon and tear gas to disperse protesters.
