Three days of intense fighting in Sri Lanka's northeast has left 420 Tamil Tiger rebels dead and pushed the remaining guerrillas into a small "no-fire" zone crowded with tens of thousands of civilians, the military said. The development is likely to raise fresh international concerns for the safety of those trapped in the area measuring just 20 square kilometers. The government offensive means the entire Puthukkudiyiruppu area, the last rebel stronghold on the edge of the safety zone in the island's northeast, is under military control, spokesman Brig. Udaya Nanayakkara said Sunday. He said the Tamil Tigers are now confined to the "no-fire" zone in a narrow strip of land along a beach. The UN estimates 150,000 to 190,000 people are trapped in the zone, with dozens dying each day. But the government says more than 23,000 civilians escaped last month and 30,000 to 40,000 still remain.