At least 52 Tamil Tiger rebels were killed in heavy fighting between troops and the guerrillas just outside their northern capital in Sri Lanka, the defence ministry said on Saturday.

Sri Lankan troops are trying to capture the northern town of Kilinochchi, where the Liberation Tigers of Tamil Eelam (LTTE) maintain their own administration, banks, police and courts and meet visiting diplomats.

Fighting on the outskirts of the town on Friday killed 52 LTTE fighters while six soldiers were wounded, the ministry said.

The Sri Lankan government, which pulled out of a Norwegian-brokered ceasefire in January, wants to capture Kilinochchi, in what would deal a major military and psychological blow to the rebels.

Army chief Lieutenant General Sarath Fonseka said Thursday his men had advanced to within four kilometres (2.5 miles) of the town, and would launch a fresh offensive next week.

On Friday, Sri Lanka's former colonial ruler, Britain, voiced deep concern about the increasing violence.

"We call on both parties to respect their obligations under international humanitarian law to enable free access for humanitarian agencies and the protection of civilians affected by the conflict," Britain's Foreign Office said.

The rebels have been fighting for an independent homeland for the Sinhalese island's Tamil minority since 1972.

Tens of thousands of people have died in the conflict.

The military also said fighting along the northern region of Weli Oya and Jaffna left eight rebels and two soldiers dead.

The LTTE did not comment on the ministry statement.

But the pro-rebel Tamilnet website said one soldier was killed when the rebels fired artillery towards the troops stationed in Jaffna on Friday.

According to a ministry toll, the LTTE have lost 6971 fighters since January. The military has said it has lost 677 soldiers in the same period.

The tolls cannot be independently verified since human rights workers and journalists are barred from visiting the warzone.

AFP