COLOMBO (AFP) - Sri Lankan troops have almost completely cornered the Tamil Tigers in their northeastern jungle base and the rebels' leader may already have fled the island, the army chief said. Lieutenant General Sarath Fonseka said his forces had surrounded the district of Mullaittivu, the last town held by the Liberation Tigers of Tamil Eelam, and hoped to totally overrun the area in the coming weeks. "We have surrounded them from all sides and the only option for them is to jump into the sea because they still have 40 kilometres of coastline," Fonseka told reporters late Saturday. He said he believed Tiger chief Velupillai Prabhakaran may already have escaped by sea. "We don't know if he is still there. He may have already fled in a boat," Fonseka said. The navy said it had stepped up a blockade along the northeastern seaboard to prevent any guerrilla movements. However, the Tigers have smuggled themselves by boat in the past. A late Tiger ideologue, Anton Balasingham and his Australian-born wife, Adele Wilby, escaped government troops in 1999 by smuggling themselves out by boat to Thailand and ended up in London. Former Tamil rebel-turned-politician Dharmalingam Sithadthan said civilians crossing front lines had said they believed the top Tiger leader may have already left the island. "He may have gone out. This is what the people think," Sithadthan said. "He could take the same route Balasingham took in 1999." However, the navy insists that it may not be possible this time. "We have a massive naval cordon in the area... and any boat that puts out of the Mullaittivu coast will be hit," navy spokesman Captain DKP Dassanayake said. The rebel chief is seen as having no safe havens overseas. The LTTE was trained and armed by New Delhi in the early 1980s but Prabhakaran, 54, is now wanted by India in connection with the 1991 murder of former Indian prime minister Rajiv Gandhi. The LTTE is also listed by the European Union and United States as a terrorist organisation. The Sri Lankan army chief said he hoped to crush the Tigers before his term ended in December 2009. "I don't think it will be that long. Hopefully it could be by the (Sinhala and Tamil) New Year (in April)," he said.