A prominent Tamil legislator was assassinated in the Sri Lankan capital Friday, while the navy said it killed six rebels in an attack on Tamil Tiger boats.

Nadaraja Raviraj, a member of the Tamil National Alliance, was leaving his house in Colombo when he was approached and shot at close range, said K. Sivajilingam, a fellow member of Parliament. Raviraj's bodyguard was also killed.

President Mahinda Rajapakse called the killing a "cowardly and heinous act" by "those opposed to dissent and political pluralism in a democratic society."

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The Tamil party blamed the government for the killing.

"We understand that a whole magazine has been emptied on them in broad daylight," said Suresh Premachandran, a Tamil National Alliance legislator. "This is a clear message to Tamil parliamentarians ... 'Don't open your mouth."'

Government spokesman Keheliya Rambukwella said it was unfair to blame the government before an inquiry takes place. He said the president had asked for help from London's Scotland Yard in investigating a series of attacks — including Raviraj's killing — which the government suspects were orchestrated by the Tamil Tigers to blame the government.

The U.S. Embassy condemned Raviraj's assassination. "It is critical that crimes such as the murder of Nadaraja Raviraj not go unpunished. We urge the government to begin an immediate investigation," the embassy said.

Raviraj, who also worked as a lawyer and was going to court when he was attacked, died at the National Hospital, said hospital director Anil Jasinghe.

Raviraj, a leading campaigner for Tamil self-rule, became mayor of the Tamil heartland Jaffna in 1999 following the assassination of his two predecessors. He was elected to Parliament as a rebel-backed representative of Tamil National Alliance in 2001 and 2004.

On Thursday, he had joined a demonstration outside the local U.N. refugee agency to call for the protection of thousands of refugees who fled their homes after military shelling killed at least 23 Tamil civilians Wednesday in the eastern Batticaloa region. The Tamil National Alliance said 41,000 Tamils were displaced.

Meanwhile, the Sri Lankan navy destroyed two Tamil Tiger naval boats early Friday, killing six rebels, said navy spokesman, Commander D.K.P. Dassanayake. A pro-rebel Web site reported the clash, but gave no casualty figures. The rebels, who often dispute government casualty figures, did not immediately comment.

A day earlier, rebels claimed they killed 25 Sri Lanka sailors and captured four in a clash in northern waters. But Dassanayake said only seven sailors were missing. There was no way to independently verify the figures.

Tamil Tiger military spokesman Rasiah Ilanthirayan said five rebels were also killed.

Military spokesman Brig. Prasad Samarasinghe said the navy, assisted by the air force, destroyed 22 of 26 rebel boats, but he did not give casualty figures.

The Tigers have been fighting since 1983 for a separate Tamil homeland in the country's north and east, citing discrimination by the majority Sinhalese.

The conflict killed more than 65,000 people before a Norwegian-brokered truce in 2002. Subsequent peace talks failed, and surging violence this year has killed more than 2,000 civilians, soldiers and rebels, threatening to plunge the country back into full-scale civil war.