Bomber hits Sri Lanka checkpoint

At least 70,000 people have been killed in the 25-year conflict

A suicide bombing near Sri Lanka's main city of Colombo has killed at least five members of the paramilitary civil defence force, military officials said.

The attacker detonated the device after gaining entry to the guard post at a security checkpoint in Wattala, just outside the city, a spokesman said.

No group has yet claimed to have carried out the bombing.

The attack comes amid a military offensive by government troops against Tamil Tiger rebels in the north.

In a separate development, the Sri Lankan navy said it had sunk a boat off the north coast of Sri Lanka, which was carrying supplies to the rebels.

Four rebels on the boat were killed, the defence ministry said.

The suicide attack near Colombo took place hours later.

"A suicide cadre has gone inside a civil defence force post in Wattala and exploded himself," said military spokesman Brig Udaya Nanayakkara.

"Due to the explosion five civil defence force people were killed and four others injured."

The army says it is nearing victory in the 25-year war with the separatist Tiger Tamils, as they close in on the key rebel stronghold of Kilinochchi.

At least 70,000 people have been killed in the conflict.