“The perpetrator was part of the JAD group that had carried out the bombing in Jolo, the Philippines,” said the police chief, referring to extremist network Jamaah Ansharut Daulah.

The bomb used in Sunday's attack was a pressure cooker bomb, Prabowo said.

Prabowo also said that four others linked to the group have been arrested in Bima, a city on the island of Sumbawa in central Indonesia's province West Nusa Tenggara.

The attack on Sunday morning killed two suspected bombers and wounded around 20 people, including some church staff members and worshippers attending mass at the time of the bombing.

A police officer stands guard near the site of an explosion outside Sacred Heart of Jesus Cathedral in Makassar, South Sulawesi, Indonesia, on Mar 28, 2021. (Photo: AP/Masyudi S. Firmansyah)

The country's chief security minister on Sunday evening also confirmed that the attack was a suicide bombing, the first official confirmation by authorities.

"A suicide bombing occurred at the cathedral church in Makassar," Coordinating Minister for Political, Legal and Security Affairs Mahfud MD told reporters in the capital Jakarta. "The two (bombers) died."

The minister said he has ordered the police and military to increase security in places of worship throughout the country.

He also urged people to be patient as authorities work to uncover the network behind the attack.

A video obtained by The Associated Press showed body parts scattered near a burning motorbike at the gates of the Sacred Heart of Jesus Cathedral in Makassar, the capital of South Sulawesi province.

Indonesian Red Cross personnel carry a body bag following an explosion outside a Catholic church in Makassar, South Sulawesi province, Indonesia on Mar 28, 2021. (Photo: Reuters/Stringer)

First batch of churchgoers were leaving church

Rev Wilhelmus Tulak, a priest at the church, said he had just finished celebrating Palm Sunday Mass when a loud bang shocked his congregation. He said the blast went off at about 10.30am as a first batch of churchgoers was walking out of the church and another group was coming in.

He said security guards at the church were suspicious of two men on a motorcycle who wanted to enter the building and when they went to confront them, one of the men detonated his explosives.

Police later said both attackers were killed instantly and evidence collected at the scene indicated one of the two was a woman.

Prabowo did not give names or say how they were identified. It was not clear if the pair were a married couple.

Police officers walk past the site of an explosion at the gate of Sacred Heart of Jesus Cathedral in Makassar, South Sulawesi, Indonesia, on Mar 28, 2021. (Photo: AP/Yusuf Wahil)

At the end of Palm Sunday Mass in St Peter’s Basilica, which opened Holy Week ceremonies at the Vatican, Pope Francis invited prayers for the victims of violence. He cited in particular “those of the attack that took place this morning in Indonesia, in front of the Cathedral of Makassar".’

Churches have been targeted in the past by extremists in Indonesia, the world's biggest Muslim-majority nation and home to several religious minorities including Christians, Buddhists and Hindus.

Indonesian President Joko Widodo said he "strongly condemned this act of terror".

"Terrorism is a crime against humanity," he said.

"I call on everyone to fight against terror and radicalism, which go against religious values."

Amnesty International said the bombing showed "complete contempt" for human rights.

JAD is an extremist group responsible for a string of attacks, including suicide bombings at churches in Indonesia's second-biggest city Surabaya in 2018.

A dozen people were killed in that attack after a family of suicide bombers driving motorbikes blew themselves up at churches during Sunday services in Surabaya.

The family - including two daughters aged nine and 12 - and another family of five, which carried out a suicide bombing on a police headquarters, all belonged to the same Koran study group. They were also linked to JAD, which has pledged allegiance to Islamic State.

An Indonesian militant and his wife - members of JAD - were also blamed for two explosions that ripped through a Catholic church on the Philippines' Muslim-majority island of Jolo in 2019, killing worshippers at Sunday mass and security forces.

Two other militants linked to that attack were shot dead by Indonesian security forces earlier this year.