Thousands of Malaysians rallying for electoral reforms met with stiff resistance from police in Kuala Lumpur, who pushed back with baton charges, water cannon and tear gas.
Police in the capital said more than 1,400 people were arrested Saturday. Most were expected to be released within a few hours.
Opposition parties said some of their leaders were also taken into custody, and at least one opposition leader suffered minor injuries.
Many of the protesters shouted slogans like “Long live the people” and carried yellow balloons and flowers.
Police barricaded many of Kuala Lumpur's streets to make it difficult for the opposition supporters to march to a rallying point at a downtown stadium.
The coalition of opposition groups behind the rally, Bersih, claimed 50,000 people took part in Saturday's demonstration, but police said the number was closer to 6,000. A news-agency from the scene estimated there were 20,000 to 30,000 people there.
Bersih is demanding Prime Minister Najib Razak's government implement electoral reforms ahead of the next round of national elections, including measures to prevent vote-buying and fraud. The elections are due to be held in 2013, but could come earlier.
A separate rally by government supporters took place simultaneously, without any police intervention.