SURABAYA, Indonesia >> Coordinated suicide bombings carried out by members of the same family struck three churches in Indonesia’s second-largest city today, police said, as the world’s most populous Muslim nation recoiled in horror from one of its worst attacks since the 2002 Bali bombings.

At least seven people plus the six family members, who included girls aged 9 and 12, died in the attacks in Surabaya, according to police. At least 41 people were injured in the attacks, which Indonesia’s president condemned as “barbaric.”

National police chief Tito Karnavian said that the father exploded a car bomb, two sons aged 18 and 16 used a motorcycle for their attack, and the mother was with her two young daughters for her attack. The woman and the two girls were all wearing explosives, Karnavian said.

Karnavian said the family had returned to Indonesia from Syria, where until recently the Islamic State group controlled significant territory.

The 2002 bombings on the tourist island of Bali, which killed 202 people in one night, mostly foreigners, are Indonesia’s deadliest terror attack. But the use of children to execute today’s attacks in Surabaya, a port city on Java island, has sent shockwaves of anger and disgust across the sprawling country.

The Southeast Asian terror network responsible for the Bali attacks was obliterated by a sustained crackdown on militants by Indonesia’s counterterrorism police with U.S. and Australian support. A new threat has emerged in the past several years, inspired by IS attacks abroad.

Experts on militant networks have warned for several years that the estimated 1,100 Indonesians who traveled to Syria to join IS posed a threat if they returned to Indonesia.

Karnavian named the father as Dita Futrianto and said he was head of the Surabaya cell of Jemaah Anshorut Daulah, an Indonesian militant network affiliated with IS that has been implicated in a number of attacks inside Indonesia over the past year. He identified the mother as Puji Kuswati.

IS claimed responsibility for today’s attacks in a statement carried by its Aamaq news agency. It didn’t mention anything about families or children taking part in the attack, and said there were only three attackers.

The attacks occurred within minutes of each other, according to Surabaya police spokesman Frans Barung Mangera.

Karnavian said Futrianto drove a bomb-laden car into the city’s Pentecostal church. Kuswati, with her two daughters, attacked the Christian Church of Diponegoro, he said.

Based on their remains, Karnavian said the mother and daughters were all wearing explosives around their waists. The family’s sons rode a motorcycle onto the grounds of the Santa Maria Church and detonated their explosives there.

A witness described the woman’s attack at the Diponegoro church, saying she was carrying two bags when she arrived.

“At first officers blocked them in front of the churchyard, but the woman ignored them and forced her way inside. Suddenly she hugged a civilian then (the bomb) exploded,” said the witness, a security guard who identified himself as Antonius.

Shattered glass and chunks of concrete littered the entrance of the Santa Maria Church, which was sealed off by armed police. Rescue personnel treated victims at a nearby field while officers inspected wrecked motorcycles in the parking lot that had been burned in the explosion.

A street merchant outside the church said she was blown several meters (yards) by the blast.

“I saw two men riding a motorbike force their way into the churchyard. One was wearing black pants and one with a backpack,” said the merchant, Samsia, who uses a single name. “Soon after that the explosion happened.”

President Joko “Jokowi” Widodo visited the scenes of the attacks and described them as “cowardly actions” that were “very barbaric and beyond the limit of humanity.”

In Jakarta, Indonesia’s capital, the Indonesian Church Association condemned the attacks.

“We are angry,” said Gormar Gultom, an official with the association, but urged people to let the police investigation take its course.

Indonesia’s two largest Muslim organizations, Nahdlatul Ulama and Muhammadiyah, also condemned the attacks.

Separately, national police spokesman Setyo Wasisto said police fatally shot four suspected militants and arrested two others early today in West Java towns. It wasn’t clear whether the shootings were connected to the church attacks.

“They have trained in order to attack police,” Wasisto said, identifying the militants as members of Jemaah Anshorut Daulah.

Jakarta police placed the capital and surrounding areas on high alert, while the transportation ministry warned airports to be on guard.

The church attacks came days after police ended a hostage-taking ordeal by imprisoned Islamic militants at a detention center near Jakarta in which six officers and three inmates died. IS claimed responsibility.

Indonesia has carried out a sustained crackdown on militants since the 2002 Bali bombings. In recent years, the country has faced a new threat as the rise of IS in the Middle East invigorated local militant networks.

Christians, many of whom are from the ethnic Chinese minority, make up about 9 percent of Indonesia’s 260 million people.