BANDUNG, Indonesia — One suicide bomber appeared to have been disguised as a churchgoer. Another drove a Toyota minivan to one attack site. Still another was seen in footage speeding on a scooter before exploding.

When the smoke cleared from the back-to-back bombings, which targeted three churches in Surabaya, Indonesia’s second-largest city, as worshipers gathered between services on Sunday morning, the police said it had been the work of one family.

A couple led their four children in a rampage that took their own lives and killed at least seven other people, investigators said.

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 back-to-back bombings as a “martyrdom’’ operation.

In a subsequent, longer media release, the group identified three modes of attack, including 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,’’ killed one person with a knife and wounded four others. Hours later, the Islamic State claimed responsibility for that attack.

More than 41 other people were wounded in the attack in Indonesia by the suicide bombers, said Frans Barung Mangera, a police spokesman. Mangera said the bombs had been detonated in different parts of the city within minutes of one another.

He said the victims included worshipers who were entering and leaving the churches between services. Two police officers were also among the victims, he said.

At a news conference later on Sunday, Indonesia’s police chief, Tito Karnavian, identified the attackers as Dita Oepriarto and his wife, Puji Kuswati. The police chief said 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.

Footage posted on YouTube showed what appeared to be one of the attackers on a scooter suddenly turning off a street and speeding toward a church before exploding.

The police said the father, driving a Toyota minivan, had dropped off the mother and the two younger children, ages 12 and 9, at the Indonesia Christian Church.

There, according to Kumparan News, an online news site, quoting the deputy police chief of Surabaya, the woman tried to force her way into the church after being stopped by a security guard.

She then detonated the bomb in the yard outside the entrance, killing herself and the two children, the deputy police chief said.

At another target, Santa Maria Church, the sons detonated the explosives, the police chief said. Photographs from the site showed several people lying on the ground outside the church gate. Other images showed scattered debris and the police cordoning off the site.

The father was behind the wheel of the vehicle that crashed into Surabaya Center Pentecostal Church, detonating explosives believed to have been in the vehicle, the police said. The couple, along with all four children, died in the explosions, the police said.

Officials in Surabaya said the police had later disabled three bombs at the home of the suspects.

Surabaya, on the eastern side of the island of Java, has a Christian minority that is about 11 percent of the city’s population of almost 3 million.

The bombings came as professed followers of the Islamic State have begun to make their presence felt in Indonesia, a Muslim-majority nation.

In 2016, the Islamic State, claimed its first attack in Southeast Asia, when militants attacked a police post and shopping center in central Jakarta, the Indonesian capital, with homemade guns and bombs.

This month, inmates who said they were followers of the Islamic State rioted in a high-security detention center outside Jakarta. Five guards were killed.