Child suicide bomber. File photo

A family of Islamist militants in Indonesia carried an eight-year-old into a suicide bomb attack against police in Surabaya on Monday, a day after another militant family killed 13 people in suicide attacks on three churches in the same city.

“The suicide bombers rode two motorbikes up to a checkpoint outside a police station and blew themselves up,’’ police chief Tito Karnavian told a news conference in Indonesia’s second-largest city.

He said that the child –a girl — survived the explosion, and CCTV footage showed the her stumbling around in the aftermath.

East Java police spokesman, Frans Barung Mangera, said four officers and six civilians were wounded in the attack.

“We hope the child will recover. We believe she was thrown three metres (10 ft) or so up into the air by the impact of the explosion and then fell to the ground,” Mangera said, adding she has been rushed to hospital.

President Joko Widodo branded the attacks in Surabaya the “act of cowards,” and pledged to push through a new anti-terrorism bill to combat Islamist militant networks.

After some major successes tackling Islamist militancy since 2001, there has been resurgence in recent years, including in January 2016 when four suicide bombers and gunmen attacked a shopping area in the capital, Jakarta.

Police suspected Sunday’s attacks on the churches were carried out by a cell of the Islamic State-inspired group Jemaah Ansharut Daulah, an umbrella organisation on a U.S. State Department terrorist list.

“In the case of Surabaya, they escaped detection, but once it happened we moved fast to identify their network.

The father of the family involved in those attacks was the head of a JAD cell in the city,” Karnavian said.

Earlier, police said his family was among 500 Islamic State sympathisers who had returned from Syria, but the police chief said that was incorrect.

During the hunt for the cell, police shot dead four suspects and arrested nine, media reported police as saying.

The police chief said the JAD cell may have been answering a call from Islamic State in Syria to “cells throughout the world to mobilise.”

He said the imprisonment of JAD’s leader, Aman Abdurrahman, could be another motive, and cited clashes with Islamist prisoners at a high-security jail near Jakarta last week in which five counter-terrorism officers were killed.

Karnavian said the JAD attacks used a powerful home-made explosive triacetone triperoxide, known as the “mother of Satan;” and commonly used in Islamic State-inspired attacks.

In another incident in Sidoarjo, south of Surabaya, police recovered pipe bombs at an apartment where an explosion killed three members of a family alleged to have been making bombs, Karnavian said.

“In all, 31 people have died since Sunday in attacks, including 13 suspected perpetrators and 14 civilians,’’ police said.