Three locally made bombs and 100 grams of ammonia were found hidden in the backyard of a mosque at Welipenna last night, police said.
The explosives were found during a joint operation carried out by the STF and the police.
Police said a 42-year-old suspect was detained over the retrieval of explosives.
Meanwhile, the police detained 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.
Police said each circuit board had the volume to contain 12 SIM cards.
They detained a 52-year old man along with the pieces.