The items found include a 2008 diary containing plans of attacks on the Sri Lankan capital and attacks carried out in the past. The diary also contained contact information on other members of the organisation.
The police said they had no reason to doubt it was the diary of the slain LTTE leader Velupillai Prabhakaran. They said all the personal details of the LTTE leader had been given in the diary.
The suspect soldier is kept under special detention orders and being further interrogated, police said.