An Indonesian family of five on Monday detonated explosives outside the police headquarters in Surabaya, a day after members of another family carried out coordinated suicide bombings on three churches which killed at least eight people.

The attack came just hours after the police announced that the family which carried out Sunday’s church bombings included girls aged 9 and 12. The police disclosed that the two families involved in both attacks knew each other.

Tito Karnavian, the nation’s National Police Chief said a girl aged about 8 who was with two of the attackers on a motorcycle survived being killed by the blast at Surabaya’s police headquarters. The explosion killed the remaining four perpetrators while six civilians and four officers were injured.

Karnavian said the father of the family that carried out the church bombings was head of the Surabaya cell of Jemaah Anshorut Daulah, an Indonesian militant network affiliated with IS that has been fingered in attacks in the country in the past year.

The flurry of attacks in Indonesia raises previous concerns that the ‘stifled’ militant networks in the world’s most populous Muslim – majority nation have been reinvigorated by the return of some of the estimated 1,100 Indonesians who had gone to fight with the Islamic State group in Syria.

Indonesia’s deadliest terror attack occurred in 2002, when bombs exploded on the tourist island of Bali, killing 202 people in one night, mostly foreigners.