A recently married couple with suspected militant links used pressure cooker bombs to blow themselves up outside a Roman Catholic cathedral during Palm Sunday Mass, Indonesian officials said Monday.

The attack wounded 20 people, including four church guards, and broke windows at the church and nearby buildings in Makassar, the capital of South Sulawesi province.

The couple were married six months ago and police were investigating their house in Makassar, National Police spokesperson Argo Yuwono said.

Police identified them only by their initials, L and his wife, YSF. Neighbors of the couple identified the man as Lukman and his wife as Dewi and said they were between 23 and 26 years old.

The attackers detonated their bombs when they were confronted by guards outside the church.

The pressure cookers contained explosive materials and nails to increase their harm to victims, said Makassar city police chief Witnu Urip Laksana.

Police carried out DNA tests to determine the attackers’ identities, Laksana said.

The couple were believed to have been members of Jemaah Anshorut Daulah, which has pledged allegiance to the Islamic State group and carried out a series of suicide bombings in Indonesia.

They included a 2016 Starbucks attack in Jakarta which killed four civilians and four militants, an attack on a bus terminal in the capital that killed three police officers and an attack on a church in Kalimantan that killed a 2-year-old girl a year later. Several other children suffered serious burns in the Kalimantan attack.

Indonesia’s last major militant attack was in May 2018, when two families carried out suicide bombings on churches in Surabaya, killing a dozen people including two young girls whose parents involved them in one of the attacks. Police said the father was the leader of a local affiliate of Jemaah Anshorut Daulah.

One of the attackers in Makassar was believed to have had links to a 2019 suicide attack that killed 23 people at Our Lady of Mount Carmel Cathedral in the Philippine province of Sulu, Indonesian National Police Chief Listyo Sigit Prabowo said.

He said the two attackers were linked to a group of suspected militants arrested in Makassar on Jan. 6, when a police counterterrorism squad killed two suspected militants and arrested 19 others. The two men who were killed were being sought for their alleged role in the Philippine attack.

Prabowo told reporters on Monday that the police elite counterterrorism squad, known as Densus 88, arrested four suspected militants believed to have links with the attackers in a raid Sunday in Bima, a city on Sumbawa island in West Nusa Tenggara province. Another suspect was arrested a day later in a separate raid in the province, he said.

The five suspects were in the same Koran study group as the two alleged attackers, Prabowo said. Before he died, the man left a will to his parents, saying goodbye and that he was ready to become a martyr, he said.

He said the counterterrorism squad on Monday also arrested four suspected militants in Condet neighborhood in eastern Jakarta. They seized five homemade pipe bombs and more than 5 kilograms (11 pounds) of chemicals for use in explosives in separate raids in the Jakarta outskirts.

The attack a week before Easter in the world’s most populous Muslim-majority nation came as the country was on high alert following the arrest in December of the leader of the militant group Jemaah Islamiyah, which has been designated a terror group by many nations.

President Joko Widodo condemned Sunday’s attack and said it has nothing to do with any religion as all religions would not tolerate any kind of terrorism. He ordered police to “thoroughly investigate the networks of the perpetrators and hunt them to the roots.”

Indonesia has been battling militants since Jemaah Islamiyah carried out bombings on the resort island of Bali in 2002 that killed 202 people, mostly foreign tourists. Attacks aimed at foreigners have been largely replaced in recent years by smaller, less deadly strikes targeting the government, police and anti-terrorism forces and people militants consider as infidels.

Since the arrest in December of Jemaah Islamiyah leader Aris Sumarsono, also known as Zulkarnaen, the counterterrorism squad has arrested more than 70 suspects, including 19 in Makassar, following a tipoff about possible attacks against police and places of worship.

Jemaah Islamiyah was once considered the preeminent terror network in Southeast Asia, but has been weakened over the past decade by a sustained crackdown. In recent years, a new threat has emerged in militants who fought with the Islamic State group in Iraq and Syria and returned to Indonesia or those inspired by the group’s attacks abroad.

(AP)