The congregation had been inside the church at the time of the explosion, South Sulawesi police spokesman E. Zulpan told Reuters. He said it was unclear whether body parts at the scene were only from the attacker.
Father Wilhemus Tulak, a priest at the church, told Metro TV that one person had been wounded holding off a suspected suicide bomber and that 10 people had been wounded in total, some of them seriously.
TVONE said the one person killed was the attacker.
Video from the scene showed police had set up a cordon around the church and cars parked nearby were damaged.
Police did not say who might be responsible for the apparent attack and there was no immediate claim of responsibility.
Police blamed Daesh-inspired Jamaah Ansharut Daulah (JAD) group for suicide attacks in 2018 on churches and a police post in the city of Surabaya that killed over 30 people.
Indonesia’s deadliest militant attack took place on the tourist island of Bali in 2002, when bombers killed 202 people, most of them foreign tourists.
In subsequent years, security forces in Indonesia, the world’s biggest Muslim-majority country, scored some major successes in tackling militancy.
But more recently there has been a resurgence of militant violence and scores of Indonesians have traveled to the Middle East to fight for Daesh.