A family including their four children carried out the suicide attacks on three churches in Surabaya, Indonesia's East Java province on Sunday, said the Police.
The death toll has risen to seven. Over forty people, including two police officers, were injured.
All the three places were bombed at around 7 a.m.
The attackers included two daughters aged 9 and 12 years old. All of the six bombers died, CNN reported.
It is believed that the parents belong to Jamaah Ansharut Daulah, a terrorist group that supports ISIS in Indonesia.
ISIS claimed responsibility for what it called "martyrdom attacks" in the port city on the east coast of Java Island, through its Amaq News Agency. But they didn't provide any proof to substantiate its claim.
The claim is not yet confirmed by the authorities.