COLOMBO (AFP) - The Sri Lankan army said on Sunday it had uncovered a large contraption that may have been intended as an underwater bunker for the leader of the Tamil Tiger rebels. The 360-foot long railway carriage-like construction may have been designed to be wheeled into the sea as a hiding place for Velupillai Prabhakaran, the army said. The bizarre unit 'could be submerged in water and used as a temporary home, it said in a statement. It was not immediately possible to verify the reported find. The govt says it is close to defeating the Tamil rebels, who are holed up on the northeast coast, after 37 years of ethnic conflict. Prime Minister Ratnasiri Wickremanayake told parliament last week that Prabhakaran, 54, was still leading his men in their battle against an overwhelming military offensive. Prabhakaran has not been seen for more than 18 months, and speculation has been rife that he may have been killed or already fled the island.