Two teenagers have been arrested and charged with terror-related offences in a territory capital within a week, allegedly glorifying a mass casualty attack at a school or place of worship.
A Darwin teenager is to appear in a children's court on Wednesday charged by the Joint Counter Terrorism Team Northern Territory with collecting or making documents likely to facilitate terrorist acts.
Another teen appeared in the same court last Thursday charged with possessing and sharing extremist material.
The charges against both teens followed a joint investigation by Australian Federal Police, Northern Territory Police and the Australian Security Intelligence Organisation.
The joint investigation began in October after police received information via Crime Stoppers about violent extremist material being posted online by an Australian user.
On Tuesday, police executed a search warrant at a Darwin home where they seized items of clothing, documents, electronic devices, and controlled and prohibited weapons.
Examination of the seized items identified material and online discussions with a "mixed ideological motivation, including glorification of mass casualty attacks at schools", police said in a statement on Wednesday.
A teenager was arrested at the home and charged with collecting or making documents likely to facilitate terrorist acts, with the maximum penalty for the offence being 10 years in prison.
AFP Commissioner Krissy Barrett said youth radicalisation may be the greatest challenge Australia faced.
''In the current climate of fraying social harmony, we are seeing more disengaged, confused, resentful and sometimes violent young people," she said.
"Some young people, impressionable and curious, are just being manipulated, and a lot of the time, it's via social media," she said.
The number of young people being investigated by counter-terrorism teams was increasing and it required a whole-of-society effort to address the issue, the commissioner said.
NT Police Commissioner Martin Dole said the identification of a second young person during the investigation was deeply concerning.
''These are serious allegations and they reinforce why we cannot afford to be complacent about violent extremism or the influences young people can encounter online," he said.
People should be alert but not alarmed, he said.
"If something concerns you, tell someone,'' he said.
"Information from the community can make an enormous difference.''
