Six members of one family were behind a wave of blasts targeting three churches in Indonesia's second city of Surabaya, police say.
At least 13 people were killed and dozens injured in the attacks, reports BBC.
A mother blew herself and two children up at one church, while the father and two sons targeted two others, police chief Tito Karnavian said.
Sunday's bombings, which the Islamic State group has claimed, are the deadliest in Indonesia since 2005.
Earlier in the day, suicide bombers attacked three churches in Indonesia on Sunday morning.
Wawan Purwanto, of Indonesia's intelligence agency, said an IS-inspired group, Jemaah Ansharut Daulah (JAD), was suspected to be behind the attacks.
ISIS's media wing also claimed responsibility for the attacks, which took place in Surabaya, a port city on the east coast of Java Island, according to CNN.
The group has not provided any proof to substantiate the claim, nor have any authorities or security sources yet verified its authenticity.
Forty-one people -- including two police officers -- were hospitalised with injuries, police spokesman Frans Barung Mangera said.