COLOMBO (AFP) -- Suspected Tamil Tiger rebels set off a roadside explosion, killing seven bus passengers and wounding 26 in northern Sri Lanka Saturday, military sources said.

The Liberation Tigers of Tamil Eelam (LTTE) set off the blast outside the town of Vavuniya, 250 kilometers (156 miles) north of Colombo, a military spokesman said. He said a soldier was among those killed. "A Claymore mine hit the bus as it was halfway through to the destination," a military official said. "The bomb was rigged up on a tree and manually triggered as the bus passed. It was the work of the Tigers."

Five people were dead on admission to Vavuniya hospital, where two passengers died because of their injuries, a hospital official said, adding that seven soldiers were among those wounded.

The attack came five days after a bomb exploded inside a bus in the east of the island, killing 17 people and wounding 25.

Saturday's bombing came despite tight security across the island's northern and eastern regions in a bid to prevent Tamil Tiger attacks.

The Tamil rebels have waged a 35-year campaign for independence that has claimed more than 60,000 lives in Sri Lanka.

More than 4,000 people have been killed in the latest upsurge of fighting that began in December 2005 despite a truce arranged in 2002.