KUALA LUMPUR, Malaysia (AP) _ The Malaysian government's sexual misconduct case against the prime minister's most prominent opponent may have been dealt a setback, and alleged police brutality against him has come under fire.

Anwar Ibrahim, who was fired by Prime Minister Mahathir Mohamad as deputy prime minister last month, was in court today to plead innocent to another charge of committing an illegal homosexual act.

With bruises on his face, he told a court Tuesday he was beaten until he fell unconscious on his first night in detention. Police said they would investigate, but Mahathir said Anwar may have inflicted the injury himself to gain public sympathy.

Anwar has pleaded innocent to 10 counts of corruption and illegal sex acts, charges he says were trumped by up his political enemies. If convicted, he could be sentenced to 20 years in prison on the sex charges and 14 years in prison on the corruption charges.

His arrest Sept. 20 sent thousands of protesters into the streets in Kuala Lumpur demanding Mahathir's resignation. The popular 51-year-old Anwar says Malaysia needs a government that is more open and less corrupt, and appears to be the strongest challenge yet to Mahathir's 17-year rule.

Making his first appearance in court Tuesday, Anwar said that after his arrest, he was led handcuffed and blindfolded to a police lockup, where he was greeted with a punch that knocked him unconscious.

Anwar also said his left eye was so swollen that he could not use it for two days after the beating. The eye was still bruised when he appeared in court.

In Washington, State Department spokesman James Foley said, ``We are deeply concerned ... by reports of police brutality during the incarceration of Anwar.''

White House spokesman Mike McCurry said President Clinton would raise human rights concerns when he visits Malaysia in November for a meeting of Asian and Pacific nations.

Amnesty International, a London-based human rights group, has called for an investigation into Anwar's treatment.

``Malaysians should be made aware of the deterioration of their fundamental liberties and the dictatorial acts of Dr. Mahathir,'' Anwar said in a message read by his wife, Azizah Ismail, to reporters outside the courthouse. Azizah said she hoped for a fair trial.

Two of the sex-related charges against Anwar stemmed from alleged relations with Munawar Anees, his former speech writer, and Sukma Dermawan, Anwar's adopted brother. Both men allegedly confessed to the acts.

Both were sentenced to six-month jail terms earlier this month, but late Tuesday both appealed their convictions. The appeals could weaken the government's case against Anwar if the two men say their confessions were coerced. No hearing dates have been set for the appeals.

Today's charge alleged that Anwar committed an illegal sex act in 1992 with his wife's tailor.

A doctor examined Anwar on Tuesday and determined his retina wasn't permanently damaged but said the wounds had come from being assaulted.

Mahathir had groomed Anwar since 1993 to succeed him, but differences between the two became stark as Malaysia's economy crumbled in the last year. The two openly differed on monetary policy and Anwar refused to allow the Finance Ministry to be used as a tool to help sagging businesses.