JAKARTA: The suicide bombing at an Indonesian cathedral on Palm Sunday was carried out by two members of a pro-Islamic State extremist group blamed for other church blasts, including a deadly 2019 attack in the Philippines, police said.

About 20 worshippers were injured by the powerful explosion outside the church in Makassar city on Sulawesi island as they celebrated the start of Holy Week.

Both suspects in the attack were killed as they rode a motorbike into the compound of the church, setting off what authorities said was an improvised explosive device known as a pressure-cooker bomb.

A church security guard tried to prevent the two perpetrators from entering when the blast occurred, they added.

Late Sunday, National Police chief Listyo Sigit Prabowo said both attackers -- a man and a woman -- were members of Jamaah Ansharut Daulah (JAD), an extremist group also blamed for a deadly church bombing in Indonesia's second-biggest city Surabaya in 2018.

Prabowo did not give names or say how they were identified, but forensic examiners were performing DNA tests on body parts scattered at the grisly scene.

"There were two perpetrators killed, one is a man and another one is a woman," Prabowo said.

"They're members of the JAD group which carried out a bomb attack in Jolo in the Philippines."

It was not clear if the pair were a married couple.

An Indonesian militant and his wife -- members of JAD -- were 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.

One witness to Sunday's bombing described hearing two "very strong" blasts and then seeing plumes of smoke, an attack that wounded about 20 church officials, congregants and security staff.

"There were several injured people on the street. I helped one woman... who was wounded and covered in blood," Yosi, who like many Indonesians goes by one name, told AFP.

"Her grandchild was also injured. There were body parts everywhere."

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.