Trouble flared after some of the crowd marched towards the hotels of delegates to the forthcoming Asia-Pacific summit.

A police motorcycle was set alight after witnesses said shots were fired in the air.

US analyst Adam Schwarz: Anwar has some high-placed friends in the US

Among the arriving delegates was the American Secretary of State, Madeleine Albright. She is scheduled to meet the wife of the sacked deputy prime minister of Malaysia, Anwar Ibrahim, who's being tried on corruption and sex charges.

Several governments have expressed disquiet over his treatment in detention.

Correspondent Simon Ingram in Kuala Lumpur says the unrest is a serious embarrassment to the Malaysian authorities who regard Mr Anwar's dismissal as a purely internal matter.

Canada snubs Malaysia over Anwar

Mr Anwar's wife is pressing her husband's case

Earlier, Mr Anwar's wife, Azizah Ismail, met a delegation of Canadian Government ministers who are in Malaysia for the Asia Pacific Economic Co-operation (Apec) forum.

Canadian Foreign Minister Lloyd Axworthy and Trade Minister Sergio Marchi met Azizah Ismail at a hotel in a show of solidarity with Mr Anwar, who Mr Axworthy described as a political detainee.

Malaysia had warned ministers attending the summit not to interfere in Malaysia's affairs.

After the meeting Azizah Ismail said: "We're very happy and encouraged."

Commenting on Ms Albright's planned meeting, Malaysian Foreign Minister Abdullah Ahmad Badawi said: "She is here as our guest. She should know what to do as our guest."

Legal challenge

Police stopped protesters who were marching to the summit venue

On Friday, Mr Anwar's lawyers filed a legal challenge over his sacking by Prime Minister Mahathir Mohamad.

They said the dismissal was an abuse of power by Dr Mahathir because only Malaysia's king, Yang di-Pertuan, has the power to formally fire ministers.

When Mr Anwar was sacked in early September, Dr Mahathir described him as being morally unfit to perform his duties.

Mr Anwar's trial on charges of corruption and sexual misconduct has been put on hold for the duration of the Apec summit.

So far only seven of the 52 prosecution witnesses have taken the stand since the trial began on 2 November.