PENANG, Malaysia - Tens of thousands of supporters cheered Malaysia's opposition figurehead Anwar Ibrahim Saturday as he launched his bid for a by-election expected to return him to parliament.

The August 26 ballot in Anwar's home state of Penang is being seen as a test of his popularity after a young male aide accused him of sodomy -- the same charge that saw him jailed a decade ago.

"I am touched by the support. This is an overwhelming support," Anwar said as he arrived at the nomination centre in the Permatang Pauh constituency which was locked down by barricades and an armed security presence.

Some 30,000 supporters shouted Anwar's battle cry of "Reformasi" or "Reform", and waved party flags, facing off against 5,000 government supporters and trading taunts and insults.

At least 3,000 police including the riot squad were deployed to keep the peace and a police helicopter hovered overhead.

"We want change. The future is Anwar. Long live Anwar!" chanted supporters of the opposition leader, a former deputy premier who was sacked in 1998 and convicted on sodomy and corruption counts widely seen as politically motivated. The sodomy conviction was later overturned.

"I am so moved by the villagers who came out so early in the morning to show their support," Anwar said as he prepared to formally register for the by-election, escorted by family members, opposition allies, and his lawyers.

Anwar, 61, has said the sodomy allegations were fabricated to prevent him from ousting the ruling Barisan Nasional coalition, after March elections that handed the opposition alliance a third of parliamentary seats.

He was formally charged earlier this month, just after his wife vacated the Permatang Pauh constituency -- which she has held since he went to jail -- to allow him to return to parliament after a decade-long absence.

Anwar, representing his Keadilan party, is running against Arif Shah Omar Shah, a veteran member of the United Malays National Organisation (UMNO) which leads the the ruling National Front coalition.

A two-term state legislator whose ability to speak Mandarin and the local Hokkien dialect is a plus in the multi-racial seat, he is nevertheless considered the underdog in a district which Anwar held from 1982-1999.

In a racial breakdown that broadly mirrors the national population, more than two-thirds of voters in Permatang Pauh are Muslim Malays, alongside Chinese who make up 26 percent and Indians at six percent.

"I have known the people here and they know what to expect from me if I am elected. I am after all a two-term assemblyman and I have been doing my work since way back," said Arif.

"I know Anwar well. We have been friends and I look forward to taking him on," he said.

Lim Kit Siang, chairman of the Chinese-based Democratic Action Party which is one of the three members of the opposition alliance, urged voters to throw their support behind Anwar.

"Permatang Pauh is in the eyes of the world now. It is their (voters') destiny to put Anwar on track to become the next prime minister," he said.

Anwar has said he is still pursuing his plan to wrest power within months, with the help of government defectors, despite the looming sodomy trial.

On Friday, Anwar's accuser Mohamad Saiful Bukhari Azlan, a 23-year-old former volunteer in the opposition leader's office, visited a mosque to swear he was telling the truth and challenged Anwar to do the same.

He also said that he was sodomised against his will, although when Anwar was formally accused in court the charge indicated the alleged sex act was consensual.

Anwar said at a rally Friday night that Saiful's action was part of the government conspiracy.

"They are afraid of me being an MP and going on to become the opposition leader in parliament," he said.

Sodomy is a serious offence in Malaysia, a conservative and predominantly Muslim nation, and carries a penalty of 20 years' imprisonment.