The separatist groups in South-east Asia pose a "clear and present danger" to Singapore, said Prime Minister Lee Hsien Loong, as Singaporeans have been drawn to fight for their causes.
Mr Lee also said that if caught, a person who joins a terrorist group overseas will be allowed to return home. "But we will make sure he has not brought back any dangerous ideas and is not likely to do any harm."
He made these points in an interview with Australia's ABC Radio National yesterday, when asked to assess the terror threat in Singapore.
"We worry about extremist terrorism a lot," he said. "The Middle East seems a long way away but it is not. This is a problem which is amidst us."
A few Singaporeans are among the Malaysians, Indonesians and others from South-east Asia that have gone to the Middle East to join the fight.
Some others from South-east Asia have also gone to southern Philippines, Mr Lee noted, and linked up with separatist groups there, including the Maute - a group that took over Marawi City last month - and the militant Abu Sayyaf group. Said the Prime Minister: "It is a clear and present danger."
The Philippines earlier said some Singaporeans were among foreign fighters in the Maute group that attacked Marawi, a largely Muslim city with more than 200,000 people. No further details were given on the Singaporeans or their alleged roles in the Maute group, which has pledged allegiance to the Islamic State in Iraq and Syria.
Separately, Singapore's Home Affairs Ministry confirmed that a Singaporean man, who has been in southern Philippines since the 1990s, has been implicated in terrorism activities there. But the ministry said there is no indication that the man, who was not identified, is involved in the ongoing insurgency.
Mr Lee also said a potential attack in Singapore "is a matter of when and not whether".
"We assume that one day, something will happen in Singapore and we are doing our best to prepare ourselves." These measures include preparing the population psychologically and making sure Singapore's multiracial society does not come under "catastrophic stress", he said.
"The risk is not just the casualties from the physical attack but the psychological damage done to the trust and confidence between people of different races and religions in Singapore, particularly between the Muslims and the non-Muslims," he added.
Toh Yong Chuan