At least 14 people were injured due to a strong blast outside a church in Indonesia's South Sulawesi province on Sunday, which was likely a suicide bombing attack carried out by two people, police said.

"The body found at the scene is believed to be of the suicide bomber," dpa news agency quoted provincial police chief Merdisyam as saying.

Two suspects were trying to enter the gate of the Sacred Heart of Jesus Cathedral in the provincial capital, Makassar, on a motorcycle when they were stopped by security guards, national police spokesman Argo Yuwono said.

Argo said 14 people were injured in the attack, including three security guards at the church.

Merdisyam earlier said that four worshippers were among the injured.

The explosion at 10.28 a.m.. was likely to have been of "high intensity," the police chief said.

"The service had finished and worshippers were coming out of the church," he said at a news conference.

The Indonesian Council of Muslim Scholars condemned the attack.

"It was a heinous act that violates the tenets of any religion," the council's deputy chairman Anwar Abbas said in a statement.

"We call on authorities to apprehend the perpetrators and mastermind of the attack," he added.

The Indonesian Communion of Churches urged Christians to remain calm.

"I call on all members of the community not to be afraid and restless," chairman Gomar Gultom said.

"Please pray for our safety."

Churches have been targeted by extremists in Indonesia several times.

In 2018, dozens of people were killed when suicide bombers committed suicide bombings at three churches during Sunday services in the city of Surabaya in East Java.