The police spokesman and Superintendent Ajith Rohana said that a man named Gunasekera Mudiyanselage Nilanga Jude Antony alias Cyril Nilangam Jude Antony is wanted.
"This man who was born in 1986 had been known in the LTTE as 'Nilango'", Rohana said.
Nilango was an active member of the LTTE in the northeastern district of Mannar's Madu area, police said.
He was responsible for creating the LTTE defences between Madu and Kanagarayankulam during the war, Rohana said.
The information on him came to light when the Madu police arrested a man named Nandarasa Saundranayagam, who was in possession of 15 kg of TNT explosives.
Defence authorities say they are on alert for the possible regrouping of the LTTE.
In early April at least three ex-LTTE cadre allegedly plotting the resurgence of the militant group were killed in a confrontation troops, officials claimed.