At least 13 killed in bombings at three churches in Surabaya carried out by members of one family, police say.

At least 13 people were killed and more than 40 wounded in separate suicide attacks by one family on three churches in Indonesia’s second-largest city.

Police said the bombings were carried out by six family members, including two young children, on Sunday in Surabaya, about 800km west of Indonesia’s capital, Jakarta. The blasts occurred minutes apart as worshippers headed into the churches for services.

“The father and one of the sons did the attack on the first church, the mother with two young children under the age of 10 committed the second attack. Two younger boys around the age of 16 committed the third attack,” Al Jazeera’s Step Vaessen, reporting from Surabaya, cited the city’s police chief as saying.

“Several more bombs were found in two different churches that didn’t explode.”

At least seven people plus the six bombers died in the attacks in Surabaya, according to police.

The bombings were the worst to target churches in Indonesia since a series of attacks on Christmas Eve in 2000 killed 15 people and wounded nearly 100.

“This act is barbaric and beyond the limits of humanity, causing victims among members of society, the police and even innocent children,” President Joko Widodo said during a visit to the scene.

#Jakarta: Suicide bombers attacked three #churches in Indonesia’s second-largest city of #Surabaya on Sunday, killing at least six people and wounding more than 35 others, police said. #indonesia pic.twitter.com/vMdfOr25I6 — Arman Sabir (@ArmanSabir) May 13, 2018

A spokesperson for the country’s intelligence agency said Sunday’s bombings were suspected to have been carried out by an ISIL-inspired group, Jemaah Ansharut Daulah (JAD).

Abu Bakar Bashir, JAD’s leader, pledged allegiance to Islamic State of Iraq and the Levant (ISIL) in 2014.

The group has committed smaller attacks over the last few years, but Sunday’s was the largest and most coordinated in Indonesia in the last decade.

National police chief Tito Karnavian said the father detonated a car bomb, two sons aged 18 and 16 used a motorcycle for their attack, and the mother and her two daughters wore explosives. He said the family had returned to Indonesia from Syria, where until recently ISIL controlled significant territory.

The wife of one of the victims said the attack took place shortly before the Sunday service was about to start.

“They were about to celebrate mass. My husband was opening doors and welcoming people,” she said.

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No church services will be allowed because the authorities suspect more attacks could happen.

The bombings come days after prisoners linked to ISIL killed five members of an elite counter-terrorism force during a 36-hour standoff at a high security jail on the outskirts of the capital.

Just this morning in Surabaya, East Java, Indonesia, 3 church are bombed pic.twitter.com/WiXY6KSmXB — ottingf (@OttingFirdaus) May 13, 2018

Bali attacks

In 2002, more than 200 people were killed in a string of bombings on the Indonesian island of Bali. The attack, carried out by a group with ties to al-Qaeda, targeted mostly tourists at popular nightclubs in the city of Kuta.

Since then, Indonesian police have arrested and killed hundreds of people with links to Jemaah Islamiyah, the group responsible for those bombings.

“Police have been celebrating sort of a victory over the last couple of years and a lot of people were more relaxed now,” Vaessen said.

Writer and journalist Michael Vatikiotis told Al Jazeera a substantial number of ISIL-members might reside in Indonesia.

“After the fall of Marawi in the southern Philippines many of them [the fighters] have probably washed back into Indonesia,” Vatikiotis said.

“On top of that, there’s probably been a greater directive from whatever is left of ISIL in Iraq and Syria to start operations in Indonesia and the Philippines,” he added.

Christian minority

Sunday’s attacks were denounced by the two largest Islamic organisations in the country, Nahdlatul Ulama and Muhammadiyah.

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In a statement, Nahdlatul Ulama said: “There is no place for terrorism, not here, not anywhere.”

The organisation also called on people to report any suspicious behaviour that might be related to any future attacks.

Although Indonesia prides itself on being a multi-religious country, Christians have been targeted more regularly in the last couple of years.

About 10 percent of Indonesia’s 261 million people are Christian. The country boasts the world’s largest Muslim population, about 227 million people.