An unidentified gunman killed a Christian priest Monday in central Indonesia, where religious tensions have been mounting since the executions last month of three Roman Catholic militants.

Rev. Irianto Kongkoli was shot in the head while shopping with his wife in Palu, the provincial capital of Central Sulawesi, said the region's police chief Brig. Gen. Badrudin Haiti.

The gunman sped off on a motorcycle with an accomplice, he said, adding that the motive of the attack was not yet clear.

Communal tensions have risen in the region since three Roman Catholic men were put to death on charges they instigated an attack on an Islamic school in 2000, killing at least 70 people.