Motorcycles burn following a blast at the Pentecost Church Central Surabaya (GPPS), in Surabaya
© Antara Foto Agency / ReutersMotorcycles burn following a blast at the Pentecost Church Central Surabaya (GPPS), in Surabaya , East Java, Indonesia May 13, 2018
At least 13 people have been killed in three seemingly coordinated suicide bombings that hit churches in the second-largest city of Indonesia, police said. Islamic state (IS, formerly ISIS) has claimed responsibility.

The suicide bombers are all members of one family, including teens and children, according to Indonesian police. The Indonesian president said the terrorists used children as suicide bombers.

"The victims are still being identified," said East Java police spokesman Frans Barung Mangera. Police say they have also secured a fourth, unexploded bomb at a church.

Around 40 victims who were injured in the attacks were transported to hospital, East Java provincial police spokesman Colonel Frans Barung Mangera told reporters, as cited by the Straits Times.

The authorities said that the attacks were carried out by a local terrorist group linked to the Islamic State (IS, formerly ISIS, ISIL). A spokesman for the country's intelligence agency said that Jemaah Ansharut Daulah was behind the blasts. The group has pledged allegiance to ISIS mastermind Abu Bakr al-Baghdadi.

The bombings are likely linked to a deadly riot in a high-security jail in Jakarta, which led to the death of five police officers and one inmate on Thursday, said Wawan Purwanto, the communication director at the intelligence agency, as reported by Metro TV. The failed prison break was claimed by IS, but authorities did not believe it was involved.

Indonesian President Joko Widodo described the attacks as "barbaric". Speaking at a press briefing on Sunday, Widodo said he instructed police "to look into and break up networks of perpetrators."

The three blasts hit on Sunday morning, within 10 minutes of each other, police said. Police have only provided details on one attack so far, which took place at Santa Maria Catholic Church.

"We have confirmed one died at the scene, one died at the hospital, two police officers were injured and there are some civilians injured," Mangera said. "In total 13 people are being treated at the hospital."

The perpetrator of the blast and a churchgoer were among the deceased at Santa Maria Church, The Jakarta Globe reported, citing police.

Two other explosions rocked the Protestant Indonesian Christian Church in Jalan Diponegoro and a Pentecostal church. Pentecostalism is a renewed movement within mainline Protestant Christianity.

Reuters reported that the death toll from the triple bombing has risen to 13 people, with at least 40 injured, according to police. It's unclear whether it includes the perpetrators of the attacks.

Christians constitute some 10 percent of the population of Indonesia, the largest Muslim-majority country in the world. There have been a number of extremist attacks on religious minorities in the country in recent years.