The secret documents were found in barrels in Vellamulliyavaikkal, 395 km northeast of the Sri Lankan capital, Colombo.
"The documents contained details of proposed rebel attacks, including suicide missions, details of arms purchases, bank transactions and plans to revamp the rebel organisation," the newspaper quoted Superintendent of Police Vass Gunawardena as saying.
The paper said, "Some 272 files have been brought to the capital and are being carefully sifted through."
Gunawardena said, "We believe that this is the most vital information we have found so far, during or after the military operations in the north." He also said the secret documents were details of the rebel network in the capital and their operation in the city.