Explosives were recovered from the backyard of a mosque at Welipenna on Friday night during a joint operation carried out by the Special Task Force and the police, reported Daily Mirror on Saturday.
The police found three locally made bombs and 100 grams of ammonia buried at the mosque.
The police said a 42-year-old suspect was arrested after the recovery of explosives.
Authorities also seized 16 circuit boards of high technology, 16 SIM cards, several compacts discs, computer accessories and a car in a house at Pirivena Mawatha in Mount Lavinia.
According to police, each circuit board had the capacity to contain 12 SIM cards. A 52-year-old man was also detained along with these items.
The recovery was made after Sri Lanka Catholic Church on Thursday cancelled Sunday masses due to fear of fresh bomb attacks.
More From This Section
The state media quoted Father Edmund Tillakaratne as saying that public masses were suspended for a second week, but a service conducted by Cardinal Malcolm Ranjith will be broadcast on the national television.
The churches across the country have been closed since the April 21 deadly coordinated Easter Sunday bombings, which killed at least 253 people and injured hundreds.