Police fired tear gas and detained more than 900 people in the capital on Saturday in a bid to prevent thousands of anti-government protesters from putting on a massive show of strength against Prime Minister Najib Abdul Razak.
Street protests are rare in the nation and foreign investors are worried that political unrest could delay economic reforms seen as essential to draw investment.
If he is put under popular pressure, Najib may reconsider a snap election and hold back on reforms such as cutting fuel
subsidies or unwinding an affirmative action programme for the country's Malay majority.
Polls are not due until 2013 but analysts have said Najib is likely to seek an early mandate after economic growth
accelerated to a 10-year high in 2010.
Reuters witnesses saw tear gas shells being lobbed at three groups of protesters in downtown Kuala Lumpur, as the crowds
chanted "Long Live the People" and "Reform".
Several people were seen bleeding after the tear gas was fired, but police gave no details of any injuries. Crowds around
the city's main bus station were also sprayed with water cannons.Might versus rights
Police said more than 600 people were taken into custody.
"We are fighting for free and fair elections," Ambiga Sreenevasan, the head of the Bersih (Clean) grouping that called
the protest, told reporters.
"The government uses might, we use our right. Our right will eventually prevail."
Bersih has vowed to bring together tens of thousands of supporters in the city's downtown area to demand electoral reforms, in what could be the biggest anti-government demonstration since Anwar Ibrahim's sacking as deputy premier in 1998 led to violent street rallies.
"We want to send a very clear message that we don't want a fraudulent electoral process," Anwar, who now heads a
three-party opposition coalition, told Reuters at a hotel near the downtown area.
Accompanied by his wife and a daughter and dressed in a yellow T-shirt, the colour of the protest movement, he said he
would join the demonstration later.
"We are not sure whether we will get to our destination. But the show must go on," he said.
The protesters had gathered around the city centre to march to a stadium in the downtown area despite police warnings that
what they were doing is illegal.
"We are not being disruptive, we want to walk for free and fair elections," said Nor Shahidal, a college student in her
early 20s, as she made her way to the national mosque.
Taxi and bus services into the city centre were halted, turning the usually busy tourist and shopping area in central Kuala Lumpur into a ghost town.
Most suburban train services were functioning, however, and areas outside the city centre were not much affected.
While Malaysia is far from being divided by political strife like its northern neighbour Thailand, the opposition has been
steadily growing more vocal.
Tens of thousands of demonstrators took to the streets at a November 2007 rally, which analysts said galvanised support for
the opposition ahead of record gains in a 2008 general election.
Najib took power in 2009, and inherited a divided ruling coalition which had been weakened by historic losses in the 2008
He has promised to restructure government and economy and introduced an inclusive brand of politics aimed at uniting the
country's different races.
Najib's approval ratings have risen from 45 percent to 69 percent in February, according to independent polling outfit
But analysts said recent ethnic and religious differences have undermined his popularity.