The rebel Liberation Tigers of Tamil Eelam (LTTE) set off the powerful Claymore mine against a bus transporting constables travelling home on leave, spokesman Prasad Samarasinghe said.

"Six policemen were killed and some more were wounded when the LTTE detonated a Claymore targeting the bus carrying police personnel on leave," Samarasinghe said. A civilian wounded in the blast died in hospital.

He said the attack was near the main university in the district of Batticaloa.

Security forces 12 days ago captured the main Tiger bastion of Vakarai town in Batticaloa district, where the guerrillas have maintained a de facto separate state for more than 10 years.

A soldier was also killed in Batticaloa on Tuesday when he stepped on an anti-personnel mine, the ministry said.

The government has vowed to crush "terrorism" after the troops captured Vakarai following weeks of fighting that officially left 45 soldiers and 331 Tigers killed.

Nearly 4,000 people have been killed in the latest surge in violence since December 2005. The violence has been escalating despite a Norwegian-arranged truce that went into effect in February 2002.