A home-made bomb went off near a church in Indonesia's restive own of Poso, Central Sulawesi province, just after midnight Saturday, causing no injury.
"It was a low explosive caused by a home-made bomb," Central Sulawesi Police spokesman M. Kilat was quoted by the country's leading news website Detikcom as saying.
"But the blast was the third in the last two months. We have increased the security profile."
Poso has become a scene of sectarian clashes between Muslims and Christians since 1999, in which thousands of people were killed.
Earlier this month, the firing squad executed three Christians who were on death row for inciting violence at a Muslim boarding school that left 60 people dead.