The police headquarters in Indonesia's second largest city was attacked Monday by suspected militants who detonated explosives from a motorcycle.

This comes just one day after members of one family killed at least eight people in suicide bombings at three churches in Surabaya.

CCTV footage shows a car and two motorcycles approaching a security checkpoint at the police complex. Then explosives from one of the motorbikes with at least two people aboard it detonates.

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

Shocking video shows two motorcyclists approaching a security checkpoint in Indonesia and detonating bombs

Police aim their weapons at a man who was being searched by other police officers following an explosion at nearby police headquarters in Surabaya

Police take a man in for questioning as they patrol around the suicide bombing

Police say the family that carried out Sunday's suicide bombings had returned to Indonesia from Syria and included girls aged nine 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.

Indonesia's president condemned Sunday's attacks as 'barbaric.'

ISIS claimed responsibility for the church attacks in a statement carried by its Aamaq news agency.

It did not mention anything about families or children taking part and said there were only three attackers.

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 counterterrorism police with US 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 IS posed a threat if they returned home.

Police say civilians and police were victims but a death or injury toll is unclear

This attack comes one day after 13 were killed in suicide bombings on three churches

An Indonesian police officer secures the area following the bomb blast at Surabaya's police headquarters

Mobile brigade police take position as they patrol outside the site of the bombing

The first of the church attacks struck the Santa Maria Roman Catholic Church in Surabaya, police spokesman Frans Barung Mangera told reporters.

That blast was followed by a second explosion minutes later at the Christian Church of Diponegoro and a third at the city's Pantekosta Church.

A witness described the woman's attack at the Diponegoro church, saying she was carrying two bags when she arrived.

'At first officers blocked them in front of the churchyard, but the woman ignored them and forced her way inside. Suddenly she hugged a civilian then (the bomb) exploded,' said the witness, a security guard who identified himself as Antonius.

Mr Mangera said three unexploded homemade bombs - two at the Pantekosta church and one at the Diponegoro church - were detonated by a bomb squad.

Shattered glass and chunks of concrete littered the entrance of the Santa Maria Church, which was sealed off by armed police.

Smoke billows from burning debris at a church in Surabaya, East Java, Indonesia May 13, 2018

Firefighters try to extinguish a blaze following a blast at the Pentecost Church Central Surabaya after suicide bombers attack three churches

Rescue personnel treated victims at a nearby field while officers inspected wrecked motorcycles in the car park that had been burned in the explosion.

A street merchant outside the church said she was blown several metres by the blast.

'I saw two men riding a motorbike force their way into the churchyard. One was wearing black pants and one with a backpack,' said the merchant, Samsia, who uses a single name. 'Soon after that the explosion happened.'

President Joko 'Jokowi' Widodo visited the scenes of the attacks and described them as 'cowardly actions' that were 'very barbaric and beyond the limit of humanity'.

In Jakarta, Indonesia's capital, the Indonesian Church Association condemned the attacks.

'We are angry,' said Gormar Gultom, an official with the association, who urged people to let the police investigation take its course.