Colombo: Suspected Tamil Tiger rebels ambushed a police bus with a roadside bomb outside a university in eastern Sri Lanka yesterday, killing six security personnel as they headed on leave and a civilian, the military said.

The attack in the restive eastern district of Batticaloa comes after the government vowed to wipe out the Tigers militarily, a development analysts say could deepen a new chapter in the two-decade civil war.

"A Claymore (fragmentation mine) attack in front of the Eastern University in Batticaloa has blasted a bus carrying police personnel going on leave," military spokesman Brigadier Prasad Samarasinghe said.

Officials said four policemen, two soldiers and a civilian had been killed, and 11 people injured. Officials had initially said six policemen were killed.

They said rebels of the Liberation Tigers of Tamil Eelam (LTTE) had sprayed gunfire after the incident before fleeing.

The Tigers were not immediately available for comment.

Yesterday's attack follows the army's capture earlier in January of a key eastern Tiger stronghold that analysts say has emboldened the government to try to end the conflict on the battlefield rather than at the negotiating table.

It also comes after two naval attacks this month blamed on the Tigers, and observers fear the government is underestimating the rebels' military capability.

The foes have ignored repeated calls by a worried international community to halt fighting and resume peace talks.

Foreign donors from the World Bank to Japan and the United States called on the government this week to come up with a devolution package to defuse the conflict, saying that increased defence spending and ruined lives were choking the economy and the island's development.

The Tigers say they do not trust the government, and have resumed their push for an independent state. Analysts expect a war that has killed more than 67,000 people since 1983 - and around 4,000 in the last year alone - to deepen.

Interpol said yesterday they had issued an international arrest warrant for the leader of the Tamil Tiger's feared naval wing, but prospects of an actual arrest look bleak.

The international police agency has issued arrest warrants for a string of senior Tigers in recent years, including the group's shadowy rebel leader, Velupillai Prabhakaran.

But the Tamil Tiger leadership is out of reach of the law in their northern stronghold and police have no way of capturing them unless they stray outside it or are defeated militarily.

"It has been revealed that Sea Tiger leader Colonel Soosai planned attacks against Sri Lankan forces and civilians, so we have issued the worldwide warrant," an official at Interpol's Colombo office said on condition of anonymity.

"He is a wanted person like Prabhakaran. Suppose he goes to any other country, they have authority to arrest him and send him back to Sri Lanka," he added.