(Updates with three soldiers killed by mine)

COLOMBO, July 3 (Reuters) - A roadside bomb and separate clash in Sri Lanka's north killed three soldiers and four Tamil Tiger rebels, the military said on Tuesday.

The soldiers were killed by a fragmentation mine, of the type commonly used by Tiger rebels, in the northern town of Vavuniya. The Liberation Tigers of Tamil Eelam (LTTE) were not immediately available for comment.

Earlier, the military said soldiers killed four rebel fighters in an overnight clash along the forward defence lines that separate government from rebel-held territory in the island's far north.

The clash in the northern Jaffna peninsula was the latest in a spree of land and sea battles, ambushes and bombings that have killed an estimated 4,500 people since a new chapter in a two-decade civil war erupted last year.

"Troops confronted the enemy by the forward defence lines in Muhamalai. Four LTTE cadres were killed," said military spokesman Brigadier Prasad Samarasinghe. "Our troops can see the bodies but have not recovered them because of mine fields."

Fighting is now focused on the north, where the Tigers run a de facto state after the government evicted them from swathes of territory they controlled in the east.

The Tigers, who see themselves as the army of the separate state they are fighting to establish, say they have now switched to guerrilla tactics and will continue to battle security forces in the east.

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