The response from police came after some protesters moved into the historic landmark Merdeka (or Independence) Square in downtown Kuala Lumpur, despite police and government warnings not to do, The Wall Street Journal reported.
Protesters dispersed, the newspaper said, and an undetermined number were detained. Protesters overturned a police car that had allegedly hit two protesters, the Journal said.
The Bersih activist group, whose name means "clean" in Malay, demands reforms to prevent fraudulent voting and alleged biases in the country's election agency and has called for international observers to monitor polls and make certain all political parties have similar access to government-controlled newspapers and broadcasters.
"Today is our day. No one can take it away from us," said Ambiga Sreenevasan, one of the co-founders of the Bersih group. "Today we speak with a clear voice: We want clean elections."
Some political analysts said the police action could weaken Prime Minister Najib Razak's attempts to portray himself as a political reformer, the Journal said.
Razak came under international criticism after police broke up a similar rally last year with tear gas and water cannons and detained about 1,600 Bersih members. After the protest, Razak pushed ahead with political reforms, including an end to the country's Internal Security Act, allowing indefinite detention without a warrant.