Police raided on Friday the office of defeated presidential candidate Sarath Fonseka as monitors and rights groups criticised the Sri Lankan election that returned President Mahinda Rajapakse to power.

The Cinnamon Gardens quarter of Colombo, where Fonseka's office is located, was cordoned off as dozens of commandos from the elite police Special Task Force searched the premises, a witness said.

Press photographers and television crews were kept away by security forces but a police officer at the scene said they were looking for "illegal material" in the compound.

Opposition spokesman Rauf Hakeem told reporters the search was an infringement of democratic rights and branded the raid government intimidation.

"This is an assault on democracy," Hakeem told reporters. "They are trying to intimidate us as we collect evidence of vote-rigging."

Fonseka was not at the office when the raid was carried out.

The raid came a day after the government accused the opposition of planning the assassination of President Mahinda Rajapakse who comfortably won a second term in Tuesday's poll in a result disputed by the opposition.

Security forces kept Fonseka under siege while election results were being announced on Wednesday and later allowed him to leave. Fonseka had expressed fears the government was trying to arrest or assassinate him.

The Hong Kong-based Asian Human Rights Commission cited alleged counting irregularities and accused Rajapakse of blatant misuse of state resources.

"Very clearly, the question as to whether Sri Lanka is any longer capable of conducting a free and fair election has been raised in this election," the group said in a statement.

"It is not only the electoral process that is under challenge. The very process of receiving, preserving and counting the ballot at the commissioner’s office itself is an issue that has been prominently raised."

Complaint, petition to be lodged

Fonseka said Thursday he had lodged a protest with the independent elections commission and would also petition the Supreme Court for an annulment of the result.

"We have already collected enough evidence of sophisticated vote-rigging at counting centres and at the time of the computer processing of the results," Fonseka said.

Official results gave Rajapakse 57.9 percent of the popular vote, trouncing the opposition-backed Fonseka, who got 40.1 percent, after a contest that many had expected to be much closer.

Rajapakse came to power in November 2005 and called Tuesday's vote four years into his six-year term in a bid to capitalise on popular support for his crushing of Tamil rebels in May that ended a 37-year separatist war.

The government insisted the election was free and fair but the United States has pressed for a probe into the charges of vote fraud.

The European Commission too issued a statement Friday calling for an investigation. Related article: EU calls for poll probe

Before polling day, the country's independent election commissioner had complained about misuse of state resources for the president's re-election campaign and bias in the state media.

Pre-election environment 'compromised'

On Thursday, a Swiss public radio reporter was asked to leave the country - a move she attributed to questions she asked at a government press conference about alleged voting irregularities.

A team of poll experts from the Commonwealth Secretariat said the election day itself had been "well-administered" but highlighted what it called a "compromised" pre-election environment.

K.D. Knight, chairman of the Commonwealth observer mission, concluded the results of the election broadly reflected the will of the people despite the violations.

"The evidence that was available to us does not suggest that the pre-election day breaches of election law would have changed the result of the count," he told AFP.

Asked about Fonseka's bid to have the result overturned, he said the opposition candidate would have to find hard evidence of malpractice to bring to the attention of the Supreme Court.

- AFP