Colombo  - The Sri Lanka Navy on Thursday destroyed a Tamil rebel boat and at least 40 guerillas were killed in a series of fierce clashes in the military's offensive to retake rebel-held areas in the north by the end of the year, military officials said.

A battle erupted between the navy and the separatist rebels off the north-western city of Nachchikudha, 380 kilometres north of Colombo, officials said.

The navy said of four rebel boats involved, three withdrew after it launched a counterattack and one was destroyed. No details of casualties were immediately available.

Government forces are trying to open up a route along the north-western coast because the main land route to the north has been closed for more than six months because of the conflict.

The military claimed it killed at least 40 rebels in multiple confrontations in fighting elsewhere in the Northern Province.

There was no independent confirmation about the fighting or the casualty figures given by the military.

About 200,000 civilians have been displaced by the fighting and are living in temporary shelters, open areas and schools.

The rebels are fighting for an autonomous homeland for Sri Lanka's Tamil ethnic minority. (dpa)