Military officials in Sri Lanka say there's been fierce fighting near the northern town of Kilinochchi between Tamil Tiger separatists and government troops advancing on their positions.

Details of casualties were unclear, but correspondents in the capital Colombo report hearing on Thursday the constant sound of ambulance sirens, as wounded soldiers -- airlifted from the battle zone -- were transported to hospitals.The army is trying to take control of the main highway between the Jaffna peninsula, which it seized from the Tamil Tigers two years ago, and the rest of the country.