Tien Chua tells the BBC what happened when he was arrested

The activist, Tian Chua, of the human rights group Suaram, said he was beaten by police officers before being released without charge.

He was detained after an anti-government demonstration in the capital Kuala Lumpur on Monday.

Matt Frei reports from Kuala Lumpur

Mr Tian is chairman of a newly formed opposition political alliance, the Coalition for People's Democracy, which is campaigning for greater political freedom in the wake of the arrest of former Deputy Prime Minister, Anwar Ibrahim.

More than 200 people were detained during the anti-government protests that followed Mr Anwar's detention.

Protest 'important'

The bruising on Anwar's face has sparked international condemnation

Mr Tian told the BBC it was important to make a protest to underline the absence of civil liberties in Malaysia, but said he did not believe there would be a serious investigation into his complaint.

"We want to tell the police force as well as the public that people who are victimised will not be silent and tolerant to their excessive action.

"I think the message is more important than the result itself," he said.

Medical report

His complaint follows the release of a medical report on injuries sustained by Mr Anwar.

Wan Azizah says the police are harassing her

The report said bruising on Mr Anwar's face was apparently caused by an assault, and not - as suggested by the Malaysian prime minister, Dr Mahathir Mohamad - self-inflicted.

Mr Anwar's wife, Wan Azizah Ismail has accused the authorities of "harassment and persecution" after she was summoned for a third time for police questioning on Thursday.

Tien Chua: "Serious doubts about the integrity of the police force"

Correspondents in Kuala Lumpur say the authorities there are keen to dissuade Wan Azizah from taking over the leadership of Malaysia's fledgling opposition movement from her husband.

Sedition charges

Wan Azizah faces possible charges of sedition after expressing fears in a television interview with CNBC Asia that her husband may be injected with the HIV virus to 'prove' charges of illegal homosexual conduct.

Her lawyer, Sivarasa Rasiah, said police had also interviewed him. "The lawyers shouldn't be subjected to this," he said, "least when they are performing their legal duties or servicing their clients.

"I think the Bar Council will have something to say about this."

International concern grows

James Wolfensohn: Anwar a close friend

Meanwhile the President of the World Bank, James Wolfensohn, who is a close friend of Mr Anwar expressed his "deep concern" at the former deputy premier's condition.

Mr Wolfensohn said it was important for the international community to continue to monitor the situation.

His comments echo those of a growing number governments and international organisations following Mr Anwar's appearance in court on Tuesday with a black eye and other bruising which he said was the result of a police beating.

James Wolfensohn, World Bank president: "As a friend of mine, of course I'm worried about him"

US Treasury Secretary Robert Rubin added to concerns already expressed by US Government.

He said Mr Anwar was "a highly respected member of the international financial community" and described him as "a great force for great good in many ways."