A suspected Tamil Tiger suicide bomber killed six paramilitary guards and wounded more than a dozen others in a residential area of Sri Lanka's capital Colombo on Sunday, officials said.

Military spokesman Brigadier Udaya Nanayakkara said the Tamil Tiger rebel targeted a security checkpoint near a market in the northern suburb of Wattala. Five people were killed at the scene, he said.

A health official said 19 people were admitted to hospital, and one person had died of injuries.

A Reuters witness said the site of the blast had been cordoned off. Military officials said those killed belonged to the civil defence force, an official organisation run by the military. The checkpoint was near a crowded market.

Earlier, the Sri Lankan navy said it had killed four rebels and destroyed a rebel boat in the north.

The military said heavy fighting continued around the rebels' self-proclaimed capital Kilinichchi in the northern war zone.

Sri Lanka's military has been closing in on Kilinochchi since September, but in the past two weeks has been assaulting heavy defences encircling the town's outskirts.

The LTTE started fighting the government in 1983. It says it is battling for the rights of minority Tamils in the face of mistreatment by successive governments led by the Sinhalese majority since Sri Lanka won independence from Britain in 1948.-Reuters