Police fired tear gas and water cannon laced with a yellow eye irritant to disperse protesters.

In a statement which he read in the High Court after the verdict, Mr Anwar called his conviction "an absolute disgrace" and accused Prime Minister Mahathir Mohamad of plotting against him.

Mr Anwar, who denied all four corruption charges, says he is the victim of a political conspiracy to topple him led by Dr Mahathir and his allies.

Soon after the verdict, hundreds of supporters marched to the courthouse, holding a banner that said: "Mahathir's frame-up. Anwar is innocent."

The BBC's David Willis: "Conviction had been long expected"

Riot police charged with batons as demonstrators retaliated with stones and bottles.

Several people were arrested including opposition leader Tian Chua, according to witnesses. Mr Chua was recently named vice president of a new party launched by Mr Anwar's wife.

Leader of the youth wing of Malaysia's ruling party Azim Zabidi: "This was a fair trial"

The conviction will bar Mr Anwar from returning to politics for at least five years.

But he has said his campaign for political reform will continue, led by his wife, Dr Wan Azizah Ismail.

Lurid evidence

Dr Wan Azizah: "We will appeal"

Mr Anwar, who was made finance minister in 1991 and deputy prime minister in 1993, is to appeal against the verdict, which came at the end of the longest trial in Malaysian history.

But he still faces another corruption charge and five counts of sodomy.

Mr Anwar appeared in court with a black eye last year

During the five-and-a-half month trial, state prosecutors argued that he was a corrupt adulterer who had abused his position to cover his tracks.

A mattress said to contain his seminal fluids was dragged into the courtroom and key witnesses testified he had had sex with women and men. His former driver said he had been Mr Anwar's "sex slave".

The defence argued that Mr Anwar was a devout Muslim and family man who was the victim of a political conspiracy to eliminate his challenge to Dr Mahathir's 18-year leadership.

'Flawed trial'

Philippine President Joseph Estrada, who sparked a diplomatic row last year after expressing support for Mr Anwar, said he was "saddened" by the conviction.

The BBC's Simon Ingram: "The sentence has left many of Anwar's supporters incensed"

"There's a saying that evil has its time but that good will always have its day,'' he added. ''Perhaps the day will come when those who are putting him down now will see the light.''

On Tuesday, a senior United Nations human rights investigator said the trial was "flawed" and did not appear to meet standards for fairness laid down in international law.

"We [are] very concerned about this trial. It has not brought any credibility for the government of Malaysia," said Param Cumaraswamy, the Malaysian UN special rapporteur for the independence of judges and lawyers.