"That video is chilling."
A relative of the 17-year-old said the teen had been brainwashed.
"What a stupid idiot," the unnamed relative told the Daily Telegraph.
"We never associated with him - that guy was brainwashed. I don't know what these kids get into.
"They don't know how to fight - they should be getting an education."
Elmir told family he was going away on a fishing trip.
Citizens who fight in foreign wars are still entitled to return to Australia if they have the appropriate documents.
The ANIC wants an inquiry into how the boy was compelled to leave Australia to fight with the group.
"It is utterly deplorable for violent extremists to use Islam as a cover for their crimes and atrocities," the Grand Mufti of Australia Dr Ibrahim Abu Mohammad said.
The ANIC has asked the federal Government to commit further resources to identify and prevent the root causes of radicalisation of Australians.
The Prime Minister said the video highlighted the global threat posed by Isis.
Isis was a threat that reached out to Australia and its allies and partners, a spokesman for Abbott said.
"That is why Australia has joined the coalition to disrupt and degrade Isil in Iraq and is giving our law enforcement and security agencies the powers and resources they need to keep Australia and Australians as safe as possible."
Labor frontbencher Tony Burke questioned how a child raised in Australia could be caught up in the terrorist group's ideology.
"I don't think anyone I've spoken to understands how that transition occurs," he said in Canberra.
Crossbench senator David Leyonhjelm described Elmir and his associates as "absolute dickheads" and "clowns".
He questioned the need for new spy agency and surveillance laws.
"They're easy to catch. We don't need new laws."
- AAP
