Indonesia was in mourning as the week began. Sunday’s savagery was brutal enough for the predominantly Muslim country to recoil in horror, roiled as it was by the worst outrage by fundamentalist Islamists since the Bali bombings in 2002.

ISIS has swiftly claimed responsibility for the butchery in three churches in the city of Surabaya, described by the country’s President as “barbaric”. Indonesia grapples with homegrown militancy and increasing intolerance towards religious minorities.

More basically, the surgical strike on Christians reaffirms that the country is posited on a communal powder-keg. The response of the Head of State might appear to be grossly inadequate ~ the attack has killed 13 people as on Monday afternoon and horror of horrors the suicide bombers comprised six members of a family, including girls aged between nine and 12.

The nature of the involvement, therefore, is testament to the degree of indoctrination at a remarkably tender age. The tragedy is no less a testament to the awesome spread of the Caliphate’s tentacles, in the aftermath of the setbacks in Iraq and Syria, buttressed by the Russian bombing from the skies.

The family that perpetrated Sunday’s attack was said to have returned to Indonesia from Syria very recently. Horrendous indeed has been the calibrated nature of the offensive driven by fanatical fury as much as calculated malevolence ~ the father is reported to have exploded a car bomb, the two sons aged 18 and 16 used a motorcycle for their attack, and the mother was with her two young daughters for her attack.

The woman and the two girls were all wearing explosives. Small wonder that the use of children as cannon fodder ~ a decidedly unusual praxis in terms of ISIS strategy ~ has sent shockwaves of anger and disgust across the country.

It is pretty obvious that the kids were in the vanguard of the assault. What will they know of the religious divide who only the joys of childhood know?

Ergo, Indonesia showcases a rare instance of fundamentalist fury. The use of children and teenagers makes the tragedy still more heart-rending. The South-east Asian terror network responsible for the Bali attacks was exterminated by a sustained crackdown on militants by Indonesia’s counter-terrorism forces, with US and Australian support.

Palpably enough, the emergence of the Islamic State of Iraq and Syria poses a new threat, a forbidding challenge. The offensive against church-goers can be contextualised with recent warnings that the estimated 1,000 Indonesians, who had relocated to Syria to join the ISIS, posed a threat if they returned to their country.

The grim foreboding turned out to be true on Sunday morning as Christians trooped into the churches in the port city of Surabaya. Christians, many of whom are from the ethnic Chinese minority, constitute about 9 per cent of Indonesia’s 260 million people. This ISIS offensive has gone beyond intra-religion strife.