Police broke up Malaysia's biggest protest in nearly two years Saturday, firing tear gas and chemical-laced water at thousands of opposition supporters demanding an end to a law that allows detention without trial.
Witnesses estimated that as many as 20,000 people took to the streets of Kuala Lumpur, defying government warnings not to participate in the rally against the Internal Security Act, which allows the indefinite imprisonment of people regarded as security threats.
The crackdown could erode support for Prime Minister Najib Razak, who took office in April and has been battling efforts by opposition parties to portray him as a leader who disregards public opinion on issues such as human rights and freedom of expression.
Kuala Lumpur police Chief Mohammed Sabtu Osman said authorities arrested 438 people after about six hours of mayhem in which riot police wielding batons chased protesters down the city's streets, scuffled with them and dragged many into detention trucks.
The protesters, some wearing opposition T-shirts and headbands, massed at the main mosque, a shopping mall and a train station.
Police fired volleys of tear gas and water mixed with stinging chemicals to disperse the crowds after they began marching toward the national palace. The protesters -- who chanted "Reformasi," the opposition's slogan for political change -- wanted to submit a petition to the constitutional monarch denouncing the security act.
"The police are really brutal," opposition leader Anwar Ibrahim told reporters at the protest. "This clearly shows Najib's intolerance to any dissent. . . . We gather here today to fight a cruel law."
Nazri Aziz, the Cabinet minister in charge of legal affairs, insisted that the government would not bow to the protesters' demands.