Anti-terror police found bombs, explosive materials, detonators, nails and books on jihad in raids on the island of Sulawesi on Wednesday, where police have reported increased militant activity in recent months.
"A total of 20 pipe-bombs and a 16-kilogram bomb housed in three Tupperware containers stuck together were found," said national police spokesman Boy Rafli Amar, adding the raids took place in the southern district of Enrekang.
Police said interrogations of suspected militants revealed several men in the group had been trained to assemble bombs and two of them were still at large, according to Mr Amar.
Police shot dead seven terror suspects and arrested four in raids last week on Sulawesi and Sumbawa islands, where the men were allegedly planning to attack holiday spots.
Another 75 kilograms of explosive materials were found in raids on Wednesday in five different locations around the popular tourist town of Tana Toraja, one of the suspected targets.
Police said the suspects were connected to a militant training camp and had been involved in killings of several police in central Sulawesi's Poso district, a known hotbed of militant activity.
Police have strengthened security in Poso since late last year after two police officers investigating a camp were found with their throats slit. Several small bomb plots were subsequently foiled.
Indonesia was rocked by a series of deadly terror attacks targeted at western tourist during the last decade.
Most of the bombings, including the 2002 Bali bombings that killed 202 people, were blamed on the Al Qaeda-linked group Jemaah Islamiyah (JI).
A crackdown on terrorism has weakened JI and key militant groups, and only low-impact attacks have been carried out in recent years by networks targeting law enforcement officers.