Singaporeans need to speak up against those who spread radical ideology and contribute to the radicalisation of others, said Home Affairs and Law Minister K. Shanmugam yesterday.

This will help to build confidence within the community in the aftermath of such news, and go beyond what religious and political leaders are already doing, he said.

Last Friday, the Ministry of Home Affairs said that Zulfikar Mohamad Shariff, 44, had been detained under the Internal Security Act last month.

The Singaporean was found to have made numerous Facebook posts that promoted and glorified terror group Islamic State in Iraq and Syria (ISIS) and its violent acts such as beheadings, the ministry said.

These postings have contributed to the radicalisation of at least two other Singaporeans.

Speaking on the sidelines of the opening of a National Kidney Foundation dialysis centre in Nee Soon South yesterday, Mr Shanmugam said: "You will get Zulfikars around the world and you will get people in Singapore who get radicalised. What we need is to make sure that the mainstream, the middle ground, is solid."

He added that, while radicalised individuals here remain in the minority, it is important for Muslims and non-Muslims to take a stand against these acts to ensure that they are kept at bay.

"Whenever there is an ISIS atrocity, an attack around the world or in the region, you have the religious, political and the community leadership speaking up. All that is good but the average person on the street needs to speak up," he said.

Zulfikar moved to Australia with his family shortly after he was in the spotlight in 2002 for challenging mainstream Muslim leaders.

The fact that he became an Australian citizen thereafter was discovered during the course of investigations, said Mr Shanmugam, who added that it is illegal under Singapore law to have dual citizenship.

"We consider him a threat to Singapore and his activities were directed at us... We will treat him as a Singapore citizen," the minister said.

He also pointed out that Zulfikar had taken part in events here, such as the Wear White movement that defends traditional family values.

Yesterday, at the launch of the Guardians of the Family programme at ITE College Central, Minister for Culture, Community and Youth Grace Fu also stressed the need to prepare the community in the face of growing terror threats.

The programme aims to raise vigilance among women, who are often the main caregivers in the family, and equip them with essential emergency skills.

About 500 women attended the event, which was held under the national SG Secure anti-terror movement.