SURABAYA, Indonesia (AP) -- Coordinated suicide bombings carried out by members of the same family struck three churches in Indonesia's second-largest city Sunday, police said, as the world's most populous Muslim nation recoiled in horror at one of its worst attacks since the 2002 Bali bombings.
At least seven people died at the churches in Surabaya along with the six family members, the youngest of whom were girls aged 9 and 12, according to police. Another 41 people were injured.
Indonesia's president condemned the attacks as "barbaric."
National police chief Tito Karnavian said that 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.
Karnavian said the family had returned to Indonesia from Syria, where until recently the Islamic State group controlled significant territory.
IS claimed responsibility for the attacks in a statement carried by its Aamaq news agency. It didn't mention anything about families or children taking part and said there were only three attackers.
Indonesia's deadliest terrorist attack occurred in 2002, when bombs exploded on the tourist island of Bali, killing 202 people in one night, mostly foreigners. But the fact that children were involved in Sunday's attacks in Surabaya shocked and angered the country.
Jemaah Islamiyah, the 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 recent 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 home.
Karnavian identified 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 attacks in Indonesia in the past year. He identified the mother as Puji Kuswati.
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 sons rode a motorcycle onto the grounds of the Santa Maria Church and detonated their explosives there.
A witness said the woman arrived at the Diponegoro church carrying two bags.
"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.
At Santa Maria, a Catholic church, shattered glass and chunks of concrete littered the entrance, which was sealed off by armed police. Rescuers treated victims in a nearby field while officers inspected wrecked and burned motorcycles in the parking lot.
A street merchant outside the church said she was thrown several 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 sites and described the attacks as "cowardly actions" that were "very barbaric and beyond the limit of humanity."
In Jakarta, Indonesia's capital, the Indonesian Church Association added its condemnation.
"We are angry," said Gormar Gultom, an official with the association, but he urged people to let the police investigation take its course.
Indonesia's two largest Muslim organizations, Nahdlatul Ulama and Muhammadiyah, also condemned the attacks.
Mangera, the Surabaya police spokesman, said police responded about 9 p.m. to an explosion in a residential building in Sidoarjo, a district bordering Surabaya.
He confirmed TV reports that three people, including a child, were inside the fifth-floor flat at the time of the blast. A bomb squad was checking the building, he said, and hundreds of people were evacuated from the neighborhood.
Separately, national police spokesman Setyo Wasisto said police fatally shot four suspected militants and arrested two others early Sunday 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 by imprisoned Islamic militants at a detention center near Jakarta in which six officers and three inmates died. IS claimed responsibility.
Despite Indonesia's crackdown on militants since the Bali bombings, the country has faced a new threat in recent years as the rise of IS in the Middle East invigorated local networks.
Christians, many of whom are from the ethnic Chinese minority, make up about 9 percent of Indonesia's 260 million people.