A day before the Islamic holy month of Ramadan, a family of four riding motorcycles loaded with explosives targeted a police station in Surabaya in an attack that injured ten people, including four police officers, according to the Jakarta Post.
The fifth and latest bomb blast comes after separate suicide attacks by one family on three churches sent shockwaves across Surabaya, about 800km west of Indonesia's capital, Jakarta.
Separately on Sunday, three members of another family were killed when homemade bombs exploded at an apartment in Sidoarjo, a town bordering Surabaya, police said. "It ordered and gave instructions for its cells to make a move", Karnavian said of the Islamic State's role in the church attacks.
"There has been an explosion, we don't know exactly what happened", he said.
Around the same time the couple's two teenage sons, aged 16 and 18, drove motorcycles to the Santa Maria Catholic Church, where they also detonated bombs.
Police have raided several locations and found more bombs. One family successfully blew up three locations.
Indonesia is home to the world's largest Muslim population, the majority of whom practice a moderate Islam.
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Gen. Tito Karnavian, chief of the National Police, said the family suspected in Sunday's attacks had recently returned to Indonesia after being deported from Syria.
Despite Indonesia's crackdown on militants since the Bali bombings, the country has faced a new threat in recent years as the rise of IS in the Middle East invigorated local networks. "One of them was a little kid", Karnavian said.
The US Embassy in Jakarta issued a statement condemning the Surabaya attacks.
The president of Indonesia, Joko Widodo, has described the attacks as "barbaric", "cowardly", and "beyond the limit of humanity". We need #GovernmentRegulationInLieuOfLawOnAntiTerrorism.Some 500 ISIS alumni who returned from Syria and Iraq are now roaming free without facing detention and deradicalization process. "The attacks yesterday are part of a pattern ... but (are among) the more sophisticated, and as it involved children, heinous".
The attack on Monday wounded at least ten people, and came a day after a wave of deadly attacks on three churches killed at least 13 people.
By Christopher WellsPope Francis assured the "dear people of Indonesia", and especially Christians in the city of Surabya, that he was "particularly close" to them in the wake of deadly attacks earlier on Sunday. Nearly 10% of the population is Christian.