Extremist terrorism remains a real and potent challenge, as underlying structures supporting terrorism are still in place, said Prime Minister Lee Hsien Loong.

Despite Al-Qaeda leaders being neutralised, the terrorist network still wields considerable ideological influence in many countries, including in Africa and Asia. PM Lee said on Tuesday: "It is adept at opportunistically exploiting local political developments to win over new sympathisers."

He added that self-radicalisation is a growing phenomenon as Jihadist sites and sermons by radical ideologues are easily available online.

He was speaking at an international conference on terrorist rehabilitation that is organised by the S. Rajaratnam School of International Studies and a group of volunteer Islamic teachers and scholars who make up the Religious Rehabilitation Group (RRG).

Addressing more than 500 participants from some 10 countries, Mr Lee said that even though Singapore has not suffered a terrorist attack in recent years, it remains a target. To thwart the terrorist threat, Singapore has to continue to deepen the trust among various ethnic groups.

Beyond building communal trust, Singapore must also build strong capabilities to act on any threat decisively. This includes tapping on the eyes and ears of the community. "We need to be able to pick up intelligence leads, pursue them thoroughly, and nip emerging threats in the bud."

Lastly, Singapore will also need to work closely with other countries as terrorism and terrorist groups "do not respect international borders".

PM Lee also commended the rehabilitation efforts by the RRG, which celebrates its 10th anniversary this year. He said that every terrorism-related detainee in Singapore who has been released from detention has undergone counselling as part of his rehabilitation. While most have since settled back with their families, found jobs and integrated back into society, several are still adjusting, and continue to be counselled by the RRG.