A Singaporean teenager allegedly planning to kill dozens of Muslims outside several mosques has been detained, the city-state’s Internal Security Department said on Wednesday.

The 17-year-old boy was detained in March, the ISD said in a statement, adding that he had regarded white supremacist Brenton Tarrant — who in 2019 had killed worshippers at mosques in New Zealand — as a “hero”.

The ISD also said he had “identified as an ‘East Asian Supremacist’”, and had decided on five mosques across Singapore for his post-Friday prayer attacks.

“This boy wanted to kill at least 100 Muslims, so that he can kill more Muslims than Tarrant had killed. He also wanted to live-stream his attacks,” Home Minister K Shanmugam told reporters.

“When he was arrested… he had already made a number of attempts to get a gun. He told ISD quite openly if he had gotten a gun, he would have carried out his attacks.”

The teen had been in online contact with 18-year-old Nick Lee, who was detained in December for having similar plans.

The multicultural country has seen several cases in recent years where young Singaporeans have been detained for allegedly making attack plans following exposure to extremist content online.

In 2024, authorities arrested a teenage boy who was allegedly planning an Islamic State group-inspired stabbing attack at a busy suburb.

In the same statement on Wednesday, the ISD also said a 15-year-old girl was placed under a restriction order in February, forbidding her from travelling nor having access to the internet without the approval of the ISD director.

It alleged that between July 2023 and December 2024, the girl was in at least eight short-term romantic online relationships with overseas-based militant Islamic State group (ISIS) supporters.

“She went to pledge allegiance to an ISIS chatbot,” said Shanmugam. “She wanted to fight and die for ISIS, she looked up flights to go to Syria, she thought of how she was going to save money to plan for her travels.”

He added that the trend of rising radicalism and extremism of young people via the internet was “concerning”.

The ISD said “self-radicalisation can happen very quickly”.

“In the case of the 15-year-old, it only took weeks,” it said, appealing for the public to “be vigilant to signs”.