Militants detonate explosives at Surabaya police headquarters in Indonesia

Monday's attack follows suicide bombings at 3 churches in the city a day earlier that killed 13 people.

The police headquarters in Indonesia’s second largest city of Surabaya was attacked on Monday by suspected militants who detonated explosives from a motorcycle, a day after suicide bombings at three churches in the city by members of one family killed at least eight people.

CCTV footage shows a car and two motorcycles approaching a security checkpoint at the police complex followed by an explosion from one of the motorbikes with at least two people aboard it.

Surabaya police spokesman Frans Barung Mangera said civilians and police were victims of the attack but didn’t immediately announce a death or injury toll.

Killer family were Syria returnees

Police say the family that carried out Sunday's suicide bombings had returned to Indonesia from Syria and included girls aged 9 and 12. All six members of the family died.

Separately on Sunday, three members of another family were killed when homemade bombs exploded at an apartment in Sidoarjo, a town bordering Surabaya, police say.

Indonesian President Joko Widodo condemned Sunday's attacks as "barbaric."

The Islamic State (IS) claimed responsibility for the church attacks in a statement carried by its Aamaq news agency. It didn't mention anything about families or children taking part and said there were only three attackers.

Terror comes revisiting

Indonesia's deadliest terrorist attack occurred in 2002, when bombs exploded on the tourist island of Bali, killing 202 people in one night, mostly foreigners. But the fact that children were involved in Sunday's attacks in Surabaya shocked and angered the country.

Jemaah Islamiyah, the network responsible for the Bali attacks, was obliterated by a sustained crackdown on militants by Indonesia's counter-terrorism police with U.S. and Australian support. A new threat has emerged in recent years, inspired by IS attacks abroad.

Experts on militant networks have warned for several years that the estimated 1,100 Indonesians who traveled to Syria to join the IS posed a threat if they returned home.