The Indonesian city of Surabaya has been targeted by a string of attacks in the past 24 hours, including suicide blasts at three churches on Sunday carried out by a single family with four children.
Another family is believed to have carried out an attack at a police station Monday morning, in which four perpetrators on two motorbikes drove into the main gateway of the building before detonating explosives, police spokesman Frans Barung Mangera said.
The four attackers died, while an eight-year-old girl who was on one of the motorcycles was thrown clear and survived. Ten people, including four police officers, were wounded in the attack.
Excluding the attackers, eight people were killed in the series of bombings Sunday, when a husband and wife used their four children in deadly suicide attacks on three Christian churches.
Rise of extremism
Indonesia, the world's most populous Muslim country, has struggled in recent months with a rise in Islamist militancy, which has come as ISIS has been squeezed out of its heartland in Syria and Iraq.
"These attacks are the nightmare scenario that's been anticipated since Indonesians affiliated with ISIS have returned from the Middle East," said Greg Barton, Chair in Global Islamic Politics at Deakin University in Australia.
Police Head General Tito Karnavian, Indonesia's top-ranking police officer, said he suspects the family that attacked the churches were members of terrorist group of Jamaah Ansharut Daulah (JAD), a main supporter of ISIS in Indonesia. Earlier reports had said the family had recently returned from Syria but Tito Karnarvian said Monday that was not the case.
The family's two young daughters, aged 9 and 12, were present when their mother detonated one of the bombs, and the couple's two teenage sons carried out a separate attack on another church. All members of the family died in the attacks.
Through its Amaq News Agency, ISIS claimed responsibility for what it called "martyrdom attacks" on the churches in Surabaya.
A government handout image shows a bomb blast at Surabaya Pantekosta (Pentecostal) Center Church on May 13, 2018 in Surabaya, Indonesia.
In a separate incident later Sunday night that police also called a terrorist attack, a bomb exploded at the Wonocolo low-cost housing complex in the city.
The bomb exploded prematurely, instantly killing a woman and her 17-year-old daughter, Barung Mangera said, adding police later found the father of the family in the house holding a detonator, and shot him.
The family's 12-year-old son took his two younger sisters to the Bhayangkara Police hospital, he said.
Mom attacks church with two daughters
In the church attack, a man identified as Dita Sopriyanto by authorities drove a van to the Indonesian Christian Church and dropped off his wife Puji Kuswat and their 9- and 12-year-old daughters, Tito Karnavian said.
The wife and daughters went inside and detonated a bomb, he added.
The father then drove the van to the city's Pentecost Central Church, where, from inside the vehicle, he detonated another bomb in front of the church.
At the same time, the general said, Sopriyanto's two sons drove motorcycles to Santa Maria Catholic Church, where they, too, detonated bombs. According to CCTV footage, the bomb at that church went off at 7:08 a.m. Sunday. (8:08 p.m. ET Saturday).
Barton at Deakin University said the Surabaya attacks could be the "opening salvo of a new, more sophisticated campaign," and added that the timing -- just before Ramadan, which begins May 15 -- "bears the hallmarks of ISIS," which has used the holy month in the past to launch high profile attacks.
"This is the first Ramadan since ISIS-linked Indonesians have returned" from Syria, he said.
Indonesia has a long history with terrorist groups, particularly the al-Qaeda affiliated group Jemaah Islamiyah, which claimed responsibility for 11 attacks between 2000 and 2010, including the deadly 2002 Bali bombings that left more than 200 people dead and hundreds injured, many of them tourists.
Formed in 2015, Jamaah Ansharut Daulah (JAD), the group blamed for Sunday's church attack, is a jihadi group that supports ISIS, according to Jakarta officials.
Its leader, Aman Abdurrahman, was scheduled to appear at a court hearing last week, but it was postponed after a deadly riot broke out at the jail where Aman is being held in Depok, West Java, according to a report in the Jakarta Post.
The militant group is part of a "second wave" of terrorist groups to be active in Indonesia, according to Hugo Brennan, senior Asia analyst at Verisk Maplecroft, a risk consultancy firm.
"The first wave was linked Al Qaeda from 2001 and were involved in the Bali attacks. Indonesian security forces dealt with them fairly effectively.
"Then in 2014 there was an uptick in violence as groups linked to ISIS became active, stoked by online propaganda, militants who traveled to the Middle East and fighting in the Philippines. The attacks yesterday are part of a pattern ... but it is one of the more sophisticated, and as it involved children, heinous."
However, he said it was "too early" to definitively link the Surabaya attacks to the riot at the jail.
The United Nations Secretary-General condemned the three terrorist attacks on the Surabaya churches. Through his spokesman, Stephane Dujarric, Secreatry General Antonio Guterres said that he was "appalled at reports that children were used to participate in the attacks," and offered his condolences to the families of the victims.
"(The Secretary General) reiterates the support of the United Nations to the Government and people of Indonesia in their efforts to fight and prevent terrorism and violent extremism, including through the promotion of pluralism, moderation and tolerance," the statement said.
More than 82% of Indonesia's roughly 261 million people follow Islam. Almost 10% of the population is Christian.