Malaysia's highest court upheld a sodomy conviction and five-year jail term on Tuesday for Anwar Ibrahim, throwing the opposition leader's political future into peril with a decision that he angrily denounced as a conspiracy.

Chief Justice Arifin Zakaria dismissed Anwar's challenge of last year's conviction for sodomizing a young male former aide, saying the court found "overwhelming evidence" of the crime.

Sodomy is punishable by up to 20 years in prison in Muslim-majority Malaysia and Anwar was expected to begin his sentence immediately.

Arifin read his judgments out to a stunned courtroom packed with journalists, opposition figures and Anwar's family and supporters, many of whom wept quietly.

Anwar later took to the dock and attacked the federal court panel of justices for taking part in a "political conspiracy" by Malaysia's government.

"In bowing to the dictates of your political masters, you have become partners to the crime," he said.

"You have chosen to be on the dark side."

Angered, the judges abruptly got up to leave, with Anwar shouting at them as they exited.

"I will not be silenced! I will never surrender!"

The UN Human Rights office and Australia said they were disappointed by the ruling.

Government critics say the case is part of a long-running campaign to destroy Anwar, a former deputy premier who was ousted from the ruling party in the late 1990s and later helped unite a previously divided and hapless opposition into a formidable force.

'Day of infamy'

"It's a day of infamy. It's a shocking decision," senior opposition parliamentarian Lim Kit Siang said.

Now 67, he would not emerge from prison until the age of 72 if he serves the full term.

Hundreds of Anwar supporters had gathered outside the court since before the ruling, chanting, "Free Anwar!" and "Reformasi!", the longtime clarion call of the movement to unseat the country's 58-year-old government.

AFP-Reuters-Xinhua