Police charged a 17-year-old boy on Tuesday with allegedly collecting manuals, guides and material promoting ISIS-inspired terrorism.
An investigation was launched after intelligence indicated an ISIS flag, destined for an inner city Melbourne address, was imported into Australia.
The teen was identified as the flag's intended recipient, the Australian Federal Police said in a statement on Wednesday afternoon.
A mobile phone and laptop were among items seized from the Melbourne home in a raid by counter-terrorism detectives on Tuesday.
The teenager has since been charged with importing a prohibited item and collecting or making documents that facilitate a terrorist act, which carries a maximum penalty of 15 years in prison.
He face a children's court, where he was remanded to reappear at a later date.
It comes as another teenager was charged with terrorism offences after he allegedly posted threats of extremist violence online.
Police initially arrested and charged the 16-year-old boy with weapons offences in December after the NSW Joint Counter Terrorism Team received reports of someone making violent threats online, federal police said.
During a search of the boy's inner-west Sydney home, police allegedly found a flick knife and a gel blaster, charging him with possessing an unauthorised pistol and a prohibited weapon.
A number of electronic devices were also seized.
While the devices were being investigated, the teenager faced court and was eventually bailed on the weapons charges.
A review of the devices allegedly uncovered violent extremist material and documents containing information that could help carry out a terror attack.
"It will be alleged the young person held a mixed ideology and outlined plans for acts of violence," federal police said.
On Tuesday, the boy was charged with five terrorism offences, including collecting and making documents likely to facilitate a terrorist act.
The weapons charges carry a maximum sentence of 14 years in jail, while the most serious of the terrorism charges have a maximum sentence of 15 years behind bars.
The teenager was expected to return to children's court on Wednesday.
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