A bomb detonated in a passenger bus in northern Sri Lanka on Monday, killing at least three passengers and wounding 35 others.
The bomb went off Monday night as the bus was traveling near the town of Vavuniya, about 210 kilometers 30 miles) north of the capital Colombo, the Defense Ministry's information center said. The bus was heading from the northwestern Mannar district to Colombo.
More details were not immediately available.
It was the third bombing of a civilian bus this month. Nearly 50 civilians have been killed in targeted attacks in the country's north and east where separatist Tamil Tiger rebels have their strongholds.
The government and the rebels have blamed each other for the attacks.
On April 1, six ethnic Sinhalese workers were gunned down in Batticaloa district while helping to build an orphanage and the next day a bomb blast inside a bus in the adjoining Ampara district killed 16 passengers.
Five days later a bus was caught in a roadside bomb blast in the Vavuniya district and eight passengers died.
Another 12 civilians both from the country's majority Sinhalese and minority Tamil communities were killed in two other attacks.
Monday's bombing comes amid rising fears that a government military offensive against the rebel-held north is imminent after weeks of near-daily air strikes and artillery fire at Tamil Tiger targets.
Earlier Monday, the Sri Lankan government ordered Norway's ambassador - the mediator of the country's collapsing peace process - to cancel a routine trip to the separatists' northern strongholds for security reasons.
Norway helped broker a 2002 cease-fire between the government and rebels, and the Scandinavian country has continued to serve as a mediator as sporadic fighting has degenerated into all-out war in the past 18 months. The cease-fire has remained officially in place as fighting has intensified.
The government has already ousted the insurgents from bases in eastern Sri Lanka, and officials say they soon plan to make a push against the Tiger's heartland in the north, where the rebels run a mini-state state complete with border guards, schools and traffic police.
The rebels, who have launched more than 200 suicide bombings in the past quarter-century, have vowed to respond to any such move with their "full capacity."
The Tigers have been fighting since 1983 for a separate homeland for Sri Lanka's 3.1 million Tamils, a largely Hindu minority concentrated in eastern and northern Sri Lanka.
At least 65,000 people were killed before the 2002 cease-fire. Air raids, bus bombings, suicide attacks and jungle clashes have left an estimated 4,000 more dead since December 2005.
Liberation Tigers of Tamil Eelam rebels have fought the government for more than two decades to carve out an independent homeland for the country's 3.1 million minority Tamils who have suffered decades of discrimination by the majority Sinhalese-dominated government of the Indian Ocean island nation of 19 million people.
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