Police in the province of Central Sulawesi on Monday said authorities detained the preacher because of his suspected links to Noordin M Top, a Malaysian accused of playing a key role in a spate of bombings in Indonesia.
Rais Adam, a police spokesman for the province, said: "A Muslim religious teacher was detained in Poso last Thursday."
He gave no details on the preacher's suspected links to Top.
A police official in Jakarta said the man had been detained under the country's anti-terrorism laws.
Top is blamed for helping to plan a series of bombings in Indonesia, including suicide attacks on three restaurants on the resort island of Bali last October that killed 20 people and attacks in Bali three years earlier that killed 202.
Police said last month that Top, already identified as a senior player in Southeast Asian militant network Jemaah Islamiah, had proclaimed himself leader of a group called Tanzim Qaedat al-Jihad, or Organisation for the Basis of Jihad.
Jemaah Islamiah is considered a regional arm of al-Qaida, and police said the new group might also have an al-Qaida link.
Police say Top is an expert in recruiting young suicide bombers among Indonesia's impoverished masses and believe that he is still in the country.