A motorcycle gunman has shot and killed the editor of a Sri Lankan newspaper that has been highly critical of the country's government.

Lasantha Wickramatunga, whose Sunday Leader newspaper has accused Sri Lankan president Mahinda Rajapaksa's government of corruption, was killed as he drove to work today in rush-hour traffic outside the capital, Colombo.

Associated Press reported that Wickramatunga was rushed to a nearby hospital for emergency surgery that lasted nearly three hours, but he died later of head wounds.

Police spokesman Ranjith Gunasekara said two gunmen rode up and opened fire on Wickramatunga. He added that an investigation had been opened but no one had been arrested.

Wickramatunga's brother Lal told Reuters that the gunman had smashed the window of his vehicle and shot at him. Footage of the crime scene broadcast on Sri Lankan TV showed bullet holes in the windshield and blood splattered over the seat of Wickramatunga's car.

The Sunday Leader is locked in a legal battle with the president's brother, Sri Lankan defence secretary Gotabaya Rajapaksa, who is suing the newspaper for defamation over stories it published alleging corruption, Reuters reported. Rajapaksa has denied any wrongdoing.

This is the second major attack on the Sri Lankan media this week, following an assault by more than a dozen gunmen on the studios of the country's biggest commercial broadcaster on Tuesday morning.

According to AP, the Sri Lankan government has denied it is behind the attacks and has appointed a committee to investigate.

In November, Amnesty International said Sri Lankan journalists face detentions and attacks, with at least 10 media employees killed since 2006.

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