Matt Frei reports from Kuala Lumpur

The doctor, quoted by news agencies, said the bruising on the former deputy premier's face was clearly the result of an assault.

The prime minister had speculated that Mr Anwar might have hurt himself to gain public sympathy, saying he "will get plenty of mileage if he showed he was abused by police."

But he said there would be an investigation into Mr Anwar's allegations.

Mr Anwar made a second court appearance on Wednesday, where he faced a further charge of sodomy.

'Dictatorial acts'

Police have cracked down hard on Anwar's supporters

Outside the court, his wife Wan Azizah Ismail read a message from him to his supporters: "Malaysians should be made aware of the deterioration of their fundamental liberties and the dictatorial acts of Dr. Mahathir," she said.

Wan Azizah said she hoped for a fair trial, adding, "I'm aware of previous political instructions from the prime minister to the judiciary."

On Tuesday Mr Anwar told a court in Kuala Lumpur that he had been beaten until he fell unconscious on the first night of his captivity on 20 September.

As well as the bruising he also complained that his vision and balance had been impaired.

International concern

BBC Correspondent Matt Frei: "International pressure increasing"

Mr Anwar's alleged treatment at the hands of the Malaysian police has sparked outrage both amongst opposition politicians and the international community.

"All Malaysians are asking how they could be safe when the former deputy prime minister could be brutally assaulted while in police custody," said Lim Kit Siang, the leader of the opposition Democratic Action party.

The Bar Council of Malaysia also said it was shocked by the police treatment and called for Mr Anwar's release.

"The assault reveals the inhumane and utter lawlessness of the action of the detaining authority," it said in a statement.

Elizabeth Wong : This is the sort of thing that happens to ISA detainees

The US State Department has called on the Malaysian Government to investigate the case and bring to justice those responsible.

The comments follow a statement by the human rights organisation, Amnesty International, condemning the treatment of Mr Anwar and calling for his immediate release.

It said the charges of against Mr Anwar were politically motivated and had no real basis.

Reform campaign

The protests are unprecedented in the country's history

Since his sacking on 2 September, Mr Anwar has led a campaign against Prime Minister Mahathir who has ruled Malaysia for 17 years.

The BBC Asia correspondent, Matt Frei, says that if the prime minister had hoped to discredit his rival and undermine the growing reform movement by bringing him to court, his tactics may now be backfiring.

The government's case against Mr Anwar may also be weakened following the decision by two men recently found guilty of being sodomised by Mr Anwar to retract their confessions and appeal against their prison terms.

Their lawyers say their confessions were obtained under duress.