A top Tamil rebel commander and three other guerrillas were killed in a mine blast in northwestern Sri Lanka Saturday as surging violence threatens to drag the island nation back to full-scale civil war. Pro-rebel Web site TamilNet reported that Lt Col Mahenthi was killed by an anti-personnel mine activated by government military in a rebel-held region of Mannar district 220 kilometers (135 miles) north of the capital, Colombo. Military spokesman Brig Prasad Samarasinghe denied army involvement saying that the soldiers do not enter rebel-controlled areas in accordance with a 2002 cease-fire agreement. Mahenthi was the second high profile rebel to be killed since May.