COLOMBO (AFP) - At least 10,000 civilians have escaped Sri Lanka's war zone in the last four days, the government said Sunday, as the president warned Tamil Tiger rebels to surrender unconditionally or be killed. The Tigers are fighting for survival after being driven back into a small patch of jungle by a military offensive that threatens to end their armed campaign for an independent ethnic Tamil homeland, launched in 1972. Two Tiger boats fleeing the fighting were attacked and sunk by the navy on Sunday off the coast of Mullaittivu, navy spokesman Captain D. K. P. Dassanayake said, adding that they recovered the bodies of two rebels. He said there were no casualties among navy sailors who had tracked the two rebel boats for over an hour before blasting them out of the water. The sea clash came as civilians were also fleeing the fighting. "Over 10,000 civilians have come to Kilinochchi while 139 others have come to Jaffna since the Independence Day (Wednesday)," the defence ministry said. "Among the rescued civilians are over 2,800 children and about 3,000 women." The ministry added that medical care, food and water was being provided at the frontlines for the fleeing civilians, who it says were among those held by the Tigers as "human shields." Many of the Tigers' cadres at the battlefront were in civilian clothing, the ministry said, adding that meant the rebels could claim that civilians were attacked when its own cadres got killed or wounded. There was no immediate reaction from the Tigers, but the pro-rebel website said that 120 civilians had been killed in two days of shelling. Claims by both sides cannot be verified because journalists, most aid groups and international observers are not allowed into the conflict zone. Hundreds of non-combatants have been killed this year, according to the International Committee of the Red Cross, and global concern has mounted that a major humanitarian crisis is unfolding away from the public's gaze. President Mahinda Rajapakse late Saturday warned the remaining rebels to surrender or face death as government forces tightened the noose. "I want to tell the Tigers: 'Lay down arms and surrender to security forces,'" the president told a rally of cheering supporters. He said the Liberation Tigers of Tamil Eelam (LTTE) " as they are formally known " had been encircled in a narrow strip of land in the north of the island and had taken thousands of civilians hostage. "They must let the civilians go and then unconditionally give themselves up," he said. "I must warn them we will not halt our operations against terrorism until we reach our final objective." The United States, European Union, Japan and Norway last week asked the rebels to lay down their arms and take part in political dialogue to end Sri Lanka's vicious unrest, which has claimed an estimated 70,000 lives since 1972. Military officials said the air force at the weekend launched further strikes on the remnants of the Tamil Tigers after successfully bombing a key rebel hideout Friday and killing at least 11 Tigers, including a top leader. The Tigers on Saturday mounted several counter-attacks in the Mullaittivu area " which until recently was their military stronghold " but security forces beat them back, according to the defence ministry. The Tigers have been restricted to an area of less than 100 square kilometres in Mullaittivu, where officials estimate 120,000 civilians are still trapped.