[BANDUNG, Indonesia] One suicide bomber appeared to have been disguised as a churchgoer. Another drove a Toyota minivan with a bomb to one attack site. Still another was seen in footage speeding on a scooter toward a church before an explosion is heard.

After the back-to-back bombings that targeted three churches in Surabaya, Indonesia's second-largest city, as worshippers gathered between services on Sunday morning, the police said they had been the work of one family: a couple who had led their four children on a terror spree that took their own lives and those of at least seven other people.

The Islamic State claimed responsibility for the attacks, according to the group's news agency Amaq. In an initial bulletin, the group described each of the bombings as a "martyrdom" operation. In a subsequent, longer media release, the group identified three modes of attack: a car bomb, a suicide vest and a motorcycle-borne bomb.

The bombings occurred one day after a man in Paris who shouted, "God is great" in Arabic killed one person with a knife and wounded four others. The Islamic State claimed responsibility for that attack. A day later, the group's news agency, Amaq, released a cellphone video of the attacker pledging allegiance to the Islamic State and calling on fellow Islamic State supporters in France, Germany, the United Kingdom and elsewhere too carry out attacks.

More than 43 other people were wounded in the suicide bombings in Indonesia, said Frans Barung Mangera, a police spokesman.

At a news conference later on Sunday, Indonesia's police chief, Tito Karnavian, said the family suspected in the attacks had recently returned from Syria: "Five hundred people were deported from Syria; among them is this family."

He identified the attackers as Dita Oepriarto and his wife, Puji Kuswati. The police chief said that two of their sons, ages 18 and 16, had also been involved. Two younger children were also seen in the company of the woman at one bombing site, the police said.

The police later disabled three bombs at the home of the suspects, officials in Surabaya said.

NYTIMES