Members of one family were behind a wave of blasts targeting three churches in Indonesia's second city of Surabaya, police say.
Indonesian police officers patrol outside a church following a suicide bomb in Surabaya. Photo: AFP or licensors
At least 11 people were killed and dozens others injured in the attack.
A mother blew herself and two children up at one church, while the father and three 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, Wawan Purwanto, of Indonesia's intelligence agency, said an IS-inspired group, Jemaah Ansharut Daulah (JAD), was suspected to be behind them.
He added that the bombings were likely to be linked to an incident earlier this month, when five members of the security forces were killed during a 36-hour standoff with militant Islamist prisoners at a high security prison on the outskirts of the capital Jakarta.
Indonesian anti-terror policemen secure the site following a suicide bomb attack outside a church in Surabaya. Photo: AFP
Visiting the scene of one of the bombings, President Joko Widodo described the attacks as "barbaric", adding that he had ordered police to "look into and break up networks of perpetrators".
This appears to be the worst attack to have been carried out by IS followers in Indonesia.
It claimed its first attack in the country in January 2016, when four civilians were killed in a series of explosions and shootings in the capital Jakarta.
In 2002, over 200 people were killed in two bombings carried out by al-Qaeda-linked militants outside a bar and nightclub on resort island of Bali.
- BBC