More than 1,400 people were arrested in Kuala Lumpur over the weekend during clashes between opposition protesters and government security forces, who reportedly used chemically laced water cannons to deter the crowd.
The demonstrations were Malaysia's most significant since 2007, and the swiftness with which Prime Minister Najib Razak cracked down suggests his government may be edgy ahead of elections to be held by 2013.
"I think you're seeing a lot of defensiveness on the part of the government," says Bridget Welsh, a Malaysia specialist at Singapore Management University. "To lock down the capital city reflects a certain degree of insecurity," she added.