Bombed: The wreck of the car that crashed into the Pentecost Church Central Surabaya, in the Indonesian city of Surabaya on Sunday. Picture: REUTERS
Bombed: The wreck of the car that crashed into the Pentecost Church Central Surabaya, in the Indonesian city of Surabaya on Sunday. Picture: REUTERS

Surabaya, Indonesia — A family of six launched suicide attacks on Christians attending Sunday services at three churches in Indonesia’s second-largest city of Surabaya, killing at least 13 people and wounding 40, officials said.

Indonesia, the world’s largest Muslim-majority country, has experienced a recent resurgence in homegrown militancy.

Police said the family who carried out Sunday’s attacks were among 500 Islamic State sympathisers who had returned from Syria.

"The husband drove the car … that contained explosives and rammed it into the gate in front of that church," East Java police spokesman Frans Barung Mangera said.

The wife and two daughters were involved in an attack on a second church, and at the third church "two other children rode the motorbike and had the bomb across their laps", Mangera said.

The daughters were aged 12 and 9 while the other two, thought to be the man’s sons, were 18 and 16, police said.

Police blamed the bombings on the Islamic State-inspired group Jemaah Ansharut Daulah. The group — an umbrella organisation on a US state department terrorist list — is estimated to have drawn hundreds of Islamic State sympathisers in Indonesia.

Islamic State claimed responsibility for the attacks in a message carried on its Amaq news agency.

"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 of the attacks.

Terrorism analyst Rakyan Adibrata said it was the first time that children had been involved in attacks in Indonesia.

East Java police spokesman Mangera said at least 13 people had been killed and 40 had been taken to hospital, including two police officers.

Streets around the bombed churches were blocked by checkpoints and heavily armed police stood guard as forensic and bomb squad officers combed the area for clues.

Television footage showed one church where the yard in front was engulfed in fire with thick, black smoke billowing up.

The attacks are the deadliest in Indonesia linked to Islamic State and the worst since October 2005, when three suicide bombers blew themselves up in Bali restaurants killing 20.

They came days after militant Islamist prisoners killed five members of an elite counter-terrorism force during a 36-hour standoff at a high-security jail near Jakarta.

Police chief Tito Karnavian said that because a large number of militant leaders had been captured "these groups are starting to … retaliate".

Wawan Purwanto, communication director at Indonesia’s intelligence agency, said that the main target of militants remained the security forces, but that "there are alternative [targets] if the main targets are blocked".

St Mary’s Catholic church, the first place of worship to be attacked, was bombed when the church was getting ready to hold a service.

An internal police report read a suspected bomb exploded in a car in the parking lot of a Pentacostal church, setting alight dozens of motorbikes. In the third location, the Indonesian Christian Church, veiled women entered the church’s yard where they were stopped by a security guard before an explosion occurred at the same spot, according to the police report.

Jeirry Sumampow, a spokesman for Indonesia’s church association, called on the government for more help for security at churches.

Pope Francis said he was "particularly close to the dear people of Indonesia, especially to the communities of Christians of the city of Surabaya, which were hit hard by the serious attack on places of worship".