The threat of self-radicalisation looms large in a digital age, as extremist propaganda spreads online. What can family members and friends do to keep their loved ones from being influenced by radical ideology, and how do you spot the warning signs?
Following the recent arrests of two self-radicalised youths, there have been calls for the community to play a part in identifying persons who might have been influenced by extremist propaganda, and to alert the authorities.
Experts said there are telltale signs that family members and friends can look out for.
Dr Munidasa Winslow, a psychiatrist at Novena Medical Centre, said this could be a sudden change, like spending more and more time on religious practices.
Typically, the individual is also likely to be withdrawn, secretive and spend a lot of time online.
Said psychologist Carol Balhetchet: "Family or friends or neighbours would say something and they would walk away or get very aggressive about it, and be very opinionated about something... The main sign is they isolate themselves and don't seem to have many friends."
Dr Lim Boon Leng, a psychiatrist at Gleneagles Medical Centre, said most of these individuals "are marginalised" and probably neglected by their parents. "They don't have people to turn to or mentor to turn to," he added.
Pasir Ris-Punggol GRC MP Zainal Sapari, a former school principal, said the "trigger point" to report someone to the authorities is knowing that he or she is sympathetic to the ideas of the Islamic State in Iraq and Syria (ISIS). "Sympathising with the ISIS cause is, I believe, the first step in terms of wanting to join in the terrorist cause," he added.
The Ministry of Home Affairs told The Straits Times that when a report is made, initial investigations will be carried out. In appropriate cases, the person may be referred for counselling and other mitigation measures without the need for arrest.
Counselling or rehabilitation programmes are tailored to the person's specific circumstances, including age, it said. Should it be necessary, the person could be arrested for further investigations. But this will depend on the extent of radicalisation, and the risk and potential threat the person poses.
What is the typical profile of a teen vulnerable to being radicalised?
Teenagers who are isolated from their families, who do not feel close to their loved ones, or who are detached from their social communities such as schools, can be easily influenced by radical ideology from terror groups such as the Islamic State in Iraq and Syria, said Dr Carol Balhetchet, a clinical psychologist and senior director for youth services at the Singapore Children's Society.
"These are the same sort of young people who would join gangs, because they do not feel committed or feel like a part of their social group," she said. "They may be loners in school or loners in their family unit. These teens are the ones who would easily fall prey to outside influence."
Dr Kumar Ramakrishna, head of policy studies at the S. Rajaratnam School of International Studies, said some young people who are unemployed or bored may also be susceptible as they seek adventure and excitement abroad.
Psychiatrist Lim Boon Leng added that teenagers can also lack the ability to understand the consequences of their actions while acting on impulse.
"The immediate gain that they see from joining an extremist group, such as the sense of glory or the reinforcement they get, are very attractive to them. They do not think about what is going to happen to them in five years or even in one year," said Dr Lim.
"It is this impulsiveness that sometimes tips them over and makes them decide to do something to prove themselves to these extremist groups."