The Malaysian authorities were braced for mass protests today after the arrest of Anwar Ibrahim, the opposition leader, for allegedly sodomising a male acquaintance – the same charge that provoked riots when it was first made ten years ago.

Road blocks were set up and water cannons and helicopters were mobilised around the police station in the Malaysian capital, Kuala Lumpur, where Mr Anwar was taken after being arrested today.

A statement posted on a website run by his office said: “Anwar Ibrahim … calls upon his supporters and the people of Malaysia to remain calm and to reject any attempts at provocation, which will give a pretext for an emergency situation to be declared.”

A warrant for the arrest of Mr Anwar the leader of the People’s Justice Party (PKR), was issued yesterday, and he was making his way to the police station voluntarily when a convoy of vehicles seized him in front of his house.

“As he entered the neighbourhood of his home, a contingent of ten police cars, half unmarked and half-patrol, forced the two cars in Anwar Ibrahim’s entourage to stop,” the New Straits Times newspaper reported on its website.

“There was a contingent of 20 balaclava-clad masked commandos who accosted him, reminiscent of the forces sent to arrest [him] at his home in September 1998.”

Three weeks ago, a 23-year-old aide to Mr Anwar filed a police report alleging that he had been forcibly sodomised by him in an apartment in Kuala Lumpur. Mr Anwar indignantly denied the claim, but briefly took refuge in the Turkish Embassy because of death threats which he reportedly received after news emerged of the allegations.

Homosexuality is illegal in Malaysia and, in 1999, Mr Anwar was sentenced to nine years in prison after being convicted of sex with his male driver. He always insisted that the charge was trumped up for political reasons by the ruling United Malay National Organisation (Umno), because of the challenge which Mr Anwar, the deputy prime minister, was planning against his boss, the then prime minister, Mahathir Mohamad.

In 2004, the conviction was overturned by Malaysia’s top court, although Mr Anwar, who was also convicted of corruption, was barred from standing for parliament until April this year. In March, however, the opposition coalition, of which he is de facto leader, achieved its greatest ever electoral success, coming close to toppling Umno and drastically undermining the leadership of the current prime minister, Abdullah Badawi.

Mr Anwar was negotiating with government supporters in the hope that they would change sides and claimed that the PK would be able to seize control of parliament in September.

Among his supporters, the latest charges will be regarded as a crude and transparent ploy to smear and foil once again Malaysia’s most brilliant leader in a generation. To his enemies, they will be further evidence of his unfitness for office in a Muslim majority country where homosexuality is regarded by many as abhorrent.

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

When Mr Anwar appeared at a Kuala Lumpur court in 1998 with bruises all over his face, public opinion around the world was outraged. Dr Mahathir claimed that Mr Anwar had inflicted the injuries on himself, but it turned out that he had been beaten up, while shackled and blindfolded, by Malaysia’s chief of police.

Mr Anwar has suffered chronic back problems since his incarceration, and has undergone extensive treatment abroad. “I feel apprehensive because my husband ... is not that well,” his wife, Wan Azizah, an opposition MP, said after his arrest. “He has a bad back, he's had surgery. And [during a] brief conversation, he said [the police] were not gentle. My concern is for my husband's safety and we want access to see him.”

Before his spectacular fall from power in 1998, Mr Anwar was regarded as one of the most promising Asian leaders, a moderate Muslim, but a deeply cultured man who was close to many western politicians and intellectuals. Gordon Brown has described him as a “good friend”.

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