Sri Lanka's Tamil Tiger rebels declared a unilateral cease-fire amid growing concern for thousands of civilians trapped amid the fighting. A rebel statement e-mailed to The Associated Press on Sunday said it would stop its military operations immediately. The rebels are cornered in a tiny strip of land on Sri Lanka's northeastern coast. The United Nations and others have called for a negotiated truce to allow civilians trapped in the sliver of territory to escape. Aid groups estimate 50,000 civilians are stuck there. There was no immediate comment from the military. But it has brushed off calls for a cease-fire, saying the rebels will use a pause to regroup.