Malaysian police arrested opposition leader Anwar Ibrahim on Wednesday on suspicion that he sodomized a male aide, pre-empting his voluntary appearance at the police headquarters to answer the allegation.

The arrest was likely to exacerbate the political divisions and tensions that have been running high in Malaysia since the opposition made unprecedented gains in the March general elections to whittle away the ruling coalition’s strength in Parliament.

Anwar has denied the sodomy accusation _ made in a police complaint by the 23-year-old male aide last month _ calling it a political conspiracy by the government to snuff out his campaign to bring the opposition to power by September.

About a dozen policemen, some of them wearing ski masks, cordoned off the road leading to Anwar’s house and stopped his car, said his lawyer Sankara Nair. He said Anwar was arrested for suspected sodomy.

Anwar was bundled into a police car with dark tinted windows and driven to the police headquarters where scores of supporters, including opposition lawmakers and his wife, Azizah Ismail, gathered.

After eight hours of interrogation, he was taken to a hospital for a medical examination, said Saiful Izham Ramli, another of Anwar’s lawyers. It was not clear why he needed to undergo an exam, he said, adding that Anwar would later be returned to police headquarters.

Meanwhile, the crowd of supporters milled around on sidewalks and on the main street, which was closed to traffic, while a heavy police presence including water cannons kept a close watch. There was no violence.

“This is not a criminal case but a political case,” said Azmin Ali, the vice president of Anwar’s People’s Justice Party, adding that the arrest was “outrageous and very uncivilized.”

Home Minister Syed Hamid Albar said the police had acted within the law.

Criminal Investigation Department chief Mohamad Bakri Zinin said in a statement that Anwar was “safe under police custody.” Zinin refused to answer questions.

Nair said he expects Anwar to be charged under a law that makes sodomy, even between consenting adults, a crime punishable by up to 20 years in jail. Anwar can be held in custody for up to 14 days as a suspect without charge.

His wife Azizah said she is apprehensive because Anwar has a bad back. She said Anwar told him in a telephone conversation that police were “not gentle” with him.

The arrest was made at about 1 p.m. as Anwar was returning home from the administrative capital of Putrajaya. He had told reporters there that he would go to the police headquarters at 2 p.m., the deadline set by the police, and give them “my fullest cooperation.”

Deputy Home Minister Wan Farid Wan Salleh said police moved in because they learned he was heading home and suspected he would not make the deadline.

“He was arrested because there is a warrant of arrest, so the police executed the warrant,” Wan Farid told The Associated Press.

The current drama recalled a similar charge Anwar faced in 1998 when he was deputy prime minister and finance minister. The accusation led to his dismissal from the government and subsequent conviction and imprisonment. His downfall led to massive street protests by his supporters for weeks.

Malaysia’s Supreme Court later overturned the conviction, but by then Anwar had served six years in jail on a related abuse of power charge. He was freed in 2004, when he revived his political career as an opposition leader.

“There is no basis for this whole fabrication and malicious attacks. It is just a repeat of the 1998 script. You can see the pattern,” Anwar said in Putrajaya.

The sodomy accusation has hampered his campaign to topple the government, which suffered badly at the hands of his three-party People’s Alliance in the March 8 general elections.

The ruling National Front coalition, which has traditionally enjoyed a two-thirds majority, now has only a 30-seat advantage over the opposition. Anwar’s charisma and strategic skills were credited with boosting the opposition’s strength in the 222-member Parliament from 19 to 82 seats.

U.S. Ambassador to Malaysia James Keith said in a statement that the arrest of a prominent opposition figure, “raises serious questions and concerns.”

“We urge Malaysian authorities to resolve this matter in a manner that enhances confidence in the rule of law in Malaysia,” he said.

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Associated Press writer Sean Yoong and Julia Zappei contributed to this report.