While IS is rapidly losing territory in Iraq and Syria, this may increase the risk of revenge attacks in Southeast Asia — and certain pockets of the region are receptive to radical Islamic ideology.

“The threat, if anything, I think has increased compared to last year and earlier this year,” K. Shanmugam told reporters.

Parts of Southeast Asia have long struggled with Islamic militancy and hundreds of radicals from the region have flocked to join IS.

Southeast Asians fighting for the jihadists have formed their own unit in the Middle East, called Katibah Nusantara, and are believed to be in regular contact with militants back home.

In the strife-torn southern Philippines, which has long battled a Muslim insurgency, a handful of Islamic extremist groups have sworn allegiance to IS.

There has been an upsurge of violence and attempted attacks in Indonesia, the world’s most populous Muslim-majority country, over the past year due to the growing influence of IS.

Even wealthy Singapore has detained several radicalised members of its local Muslim minority.

“There is an increased likelihood that the Islamic State will declare an official wilaya, or province, in Southeast Asia in 2017,” Otso Iho of defence analysts IHS Janes said Wednesday.

This would “most likely” happen in the southern Philippines, he added.

The region suffered its first IS attack in January this year when extremists launched a deadly suicide bombing and gun assault in Jakarta.

Minister Shanmugam said one key challenge for Singapore, an immigrant society of 5.5 million people, would be maintaining social cohesion in the aftermath of an attack.

Pointing to successful attacks in neighbouring Malaysia and Indonesia, Shanmugam said it was a matter of when — not if — an attack would hit Singapore.

“We will guard our borders but the risk is quite significant,” he said.