Anti-terrorist squads stand guard outside the bombing site at Santa Maria church in Surabaya, capital of Indonesia's East Java Province, on May 13, 2018. (Photo: Xinhua/ VNA)

The explosion happened after suicide bombings in three churches in Surabaya, Indonesia’s second-largest city, killed at least 14 people and wounded dozens others in a coordinated attack police said was carried out by one family and their children. Indonesian police chief, Tito Karniavan, told reporters that investigators believed one family – a husband and wife, and their four children aged between nine and 18 – were the perpetrators of the worst attack the country has seen in more than a decade. The police of Indonesia’s East Java province said the family was among 500 Indonesians who have returned from Syria and who may have ties to the Islamic State.

Many areas in Indonesia including Jakarta, Riau, East Java and Bali have been put on high alert following the bombing.