Two Singaporean teenagers radicalized by the Islamic State group were arrested by local authorities on terrorism-related charges, officials said Wednesday.

One of them, 19-year-old student M. Arifil Azim Putra Norja'i, had made plans to join ISIS abroad, the Straits Times reported, citing Singapore's ministry of home affairs (MHA). Authorities reportedly said that he had planned to conduct terror attacks in Singapore if he failed in his pursuit to travel to Syria to fight alongside the militant group. He was arrested in April. 

The second was an unnamed 17-year-old who was arrested earlier this month.

Arifil is the first-known case of a self-radicalized citizen of Singapore plotting a local terror attack, authorities said. Investigators reportedly said that he began viewing terrorist propaganda online in 2013, after which he grew to support the extremist ideology. 

"Fortunately, another person who knew Arifil noticed the changes in him, and had brought him to the attention of the authorities, who were then able to investigate the matter and take action before he could carry out his violent attack plans in Singapore," the MHA statement reportedly said.

Deputy Prime Minister and Minister for Home Affairs Teo Chee Hean warned that Singapore faces a significant threat from radicalization like other countries in the region, and called on family, friends and public institutions to help counter the extremist ideology.

"Our community leaders have worked hard to counter radical ideology. And we should all, from all communities in Singapore, support one another. ... If you know or suspect anyone who is becoming radicalized, please notify the authorities early," he said, according to the Straits Times. "You may be helping to save that person from harming himself and others."

Deputy Chairman of the Home Affairs and Law Committee Edwin Tong reportedly said that youth were especially vulnerable. "Youths today are very impressionistic, not yet mature enough to differentiate what are ideals and what is practical and reality.

"It's about being close to them, know what they are reading online, and observing any change of behavior," he said.

Over 12,000 foreign fighters have traveled to Syria from at least 81 countries to join ISIS and similar groups, according to a June 2014 study. The typical profile of a foreign fighter is a young man aged between 18 and 29, although women and many younger people including teenagers have been radicalized as well. Teo warned in 2014 that a small number of Singaporeans, including one woman, were known to be fighting in Syria.