RANCHO MIRAGE (California) — South-east Asia has become a fertile ground for terrorism, and while it is unlikely for followers of the Islamic State (ISIS) to overturn governments in the region, the terror group could still set up a base and that would pose serious problems, said Prime Minister Lee Hsien Loong.

“They think, or some of their followers think, that they can overturn governments in South-east Asia and set up a caliphate. It’s a fantasy,” Mr Lee said. “But it is not such a fantasy for them to think and to work at setting up a wilayat in South-east Asia, a province and authority, a place somewhere in South-east Asia which is ISIS territory, just like they have territory in Syria and Iraq.”

Mr Lee added that this is because South-east Asia is a big place and there are areas where government writ does not run as strongly. “In such a place ISIS can take root, and establish a base and that will create serious problems for all of us,” he added.

Mr Lee was speaking at a closed-door retreat on the second day of a special United States-ASEAN summit in Sunnylands, California.

Noting that terrorism affects everyone, Mr Lee suggested two ways to tackle the ISIS threat in the region: Strengthen international cooperation and counter the spread of extreme exclusivist ideologies.

“A terrorist does not know any borders. Theirs is a multinational endeavour, so too must our anti-terrorist cooperation go beyond borders,” he said, adding that Singapore has readily participated in the international counter-ISIS coalition.

The spread of extreme, exclusivist ideologies, which breed enmity and which ultimately lead to violence, must also be countered, said Mr Lee. He noted that Singapore works closely with religious and community leaders to reach out to the wider society so that, collectively, a firm stand will be taken against exclusivist ideas.

“It is hard to imagine how people, in the name of religion, can go out and kill others — hundreds, thousands or even more — and to believe that such a killing makes yourself a martyr, and that you are doing the will of God and will go to heaven,” he said. “But these crazy ideas have taken root and they have spread, and we have to stop them.”

Mr Lee added that this was why Singapore organised a regional symposium on religious rehabilitation and social reintegration.

“The ultimate aim of terrorism is to make a sharp and violent divide between ‘us’ and ‘them’. But if we strengthen our cooperation, if we band together to counter their ideology and take a firm, united stand, I am confident that they will not prevail, and eventually we will defeat terrorism,” he said.

Besides terrorism, the threat of climate change was also addressed by Mr Lee at the retreat, which focused on protecting peace, prosperity and security in the Asia-Pacific region.

“Whether it is high temperatures, more erratic temperature patterns, droughts and floods, or melting ice caps, raising sea levels around the world, it is already here, it is affecting us more severely than the current consensus projections,” said Mr Lee.

“Singapore takes the challenges of climate change very seriously because climate change can affect us in a very major way.”

He said decisive action must be taken and called on all parties to follow through on the global climate change accord reached in Paris late last year.

“The Paris Climate Agreement last December was significant. Scientifically, it is a modest step,” Mr Lee said. “But politically, it was hugely significant because it signals the resolve of the international community to do something. It is a start and will be the springboard for something substantial which will make a bigger difference.” He added that he hoped the US will continue to play a lead role on the issue.

“Without US leadership, no other country will reach a deal, much less implement an agreement. But if we do and implement the agreement, then we can ensure the sustainability of our environment and make the world a better place for our children,” said Mr Lee.