Bazuki Muhammad / Reuters
A protester is led away by his companions during clashes with police in Kuala Lumpur, Saturday.
Updated at 7:05 a.m. ET: Riot police fired tear gas and water cannon on Saturday at a crowd of up to 25,000 protesters who had converged on the center of the Malaysian capital Kuala Lumpur to demand changes to an electoral system.
Demonstrators also battled with police at a train station nearby, throwing bottles at officers who responded by firing tear gas rounds.
Thousands who had been confronting police outside the city's historic Merdeka Square were scattered after riot police fired water cannon and then at least 10 rounds of tear gas into the crowd. The police said they had been forced to react after protesters tried to force their way through barriers and enter the square.
The violence could carry political risks for Prime Minister Najib Razak if it is seen as unjustified, possibly forcing him to delay elections that must be called by next March but which could be held as early as June. Najib's approval rating tumbled after July last year when police were accused of a heavy handed response to the last major electoral reform rally by the Bersih (Clean) group.
Bazuki Muhammad / Reuters
A protester with a message taped over his mouth takes part in the Bersih (Clean) rally near Independence Square in Kuala Lumpur, Saturday.
"They asked the crowd to disperse but did not give enough warning," said Aminah Bakri, 27, with tears streaming down her face from the tear gas exposure.
Police shut down much of the city center and enforced a court order that the protesters should not enter the symbolically important Merdeka Square.
The Bersih (Clean) group that is leading the protest earlier said it would obey the ban but will march as close as possible to the square, raising the possibility of a repeat of violent clashes that marred Bersih's last major protest in July 2011.
"Now it looks like we will have to fight for our right to gather at Merdeka Square as well as fight for free and fair elections," said Muhammed Hafiz, a 28-year-old store clerk who was preparing to join the protest.
Organizers hoped the protest will draw 100,000 people, including thousands demonstrating against a controversial rare earths plant being built by Australian firm Lynas on the country's east coast. That would make it the biggest protest since the "Reformasi" (Reform) demonstrations in 1998 against then Prime Minister Mahathir Mohamad.
Bazuki Muhammad / Reuters
Protesters of the Bersih (Clean) group shout slogans near Dataran Merdeka, also known as Independence Square, in Kuala Lumpur, Saturday.
A police official estimated the protesters numbered 15,000 to 20,000 by midday with just one arrest reported.
The protest is a delicate challenge for the government of Prime Minister Najib Razak, possibly affecting the timing of elections that he is preparing to call as early as June.
Najib must be mindful of conservatives in his party who are wary that his moves to relax tough security laws and push limited election reforms could threaten their 55-year hold on power.
Last July's rally, more than 10,000-strong, ended in violence when police fired tear gas and water cannons at the yellow-shirted protesters, drawing criticism of a heavy-handed response and sending Najib's popularity sliding. His approval rating has since rebounded to 69 percent, according to one poll.
Police helicopters buzzed overhead on Saturday morning as protesters gathered. Reuters correspondents saw about 200 riot police stationed in the square and five water cannons heading to the site where Malaysia declared independence from Britain.
Mark Baker / AP
Police move to try and stop a group of protesters as they march through the central business district in Kuala Lumpur, Malaysia, Saturday.
Bersih, an independent movement whose goals are backed by the opposition, has a history of staging influential rallies as Malaysians have demanded more freedoms and democratic rights in the former British colony that has an authoritarian streak.
The National Front is trying to recover from its worst ever election result in 2008 when it lost its two-thirds majority in parliament, giving the diverse, three-party opposition led by former finance minister Anwar Ibrahim real hope of taking power.
Najib has replaced tough security laws - ending indefinite detention without trial - relaxed some media controls, and pushed reforms to the electoral system that critics have long complained is rigged in the government's favor. A bipartisan parliamentary committee set up by Najib this month issued 22 proposals for electoral reform, including steps to clean up electoral rolls and equal access to media.
However, the government gave no guarantee that any of the steps will be in place for the next election.
Reuters contributed to this report.
More world news from msnbc.com and NBC News:
- Has the Taliban fallen on tough times?
- Blind Chinese activist Chen Guangcheng escapes from house arrest
- US offers 'safe passage' to Afghan Taliban leaders
- Up in smoke: Netherlands aims to ban foreigners from buying pot
- UK spy death: 'Even Houdini' could not have locked himself in bag
- 68,000 guns seized in Mexico since 2006 came from US
Follow us on Twitter: @msnbc_world