Police block off a street ahead of the arrival of demonstrators demanding the closure of the Parramatta Mosque in western Sydney.

Australian police revealed on Thursday that a 12-year-old is on the radar of counter-terrorism authorities as Prime Minister Malcolm Turnbull urged closer cooperation with Muslim leaders to combat a growing extremist threat.

The boy was listed on a federal court order among a group of males that may have helped Farhad Jabar, 15, who shot a police employee in the back of the head in Sydney earlier this month while reportedly shouting religious slogans.

“We’re shocked that a 12-year-old is on police radar for these types of matters,” Australian Federal Police Commissioner Andrew Colvin told the Australian Broadcasting Corporation.

“This threat has evolved, it’s become younger.” He added that “the problem is getting worse for Australia, not better”.

“The numbers of individuals that we’re concerned about overseas has plateaued a little.

“Some very good work is being done by our border agencies and our police and security agencies to stop people from leaving for the conflict zones, but there’s no doubt that this problem is becoming more acute and more difficult.”

Earlier this week, Canberra outlined plans to tighten counter-terrorism laws further, including restricting the movements of suspects as young as 14 in the wake of the deadly attack by Jabar on police employee Curtis Cheng. Jabar was killed by police fire soon after.

Justice Minister Michael Keenan also expressed alarm at the age of children being targeted for radicalisation but declined to say how many under 14 were on watch lists.

“I do not think it is appropriate for me to go into that,” he said.

Authorities lifted Australia’s terror threat alert to high a year ago, introduced new national security laws and have since conducted several counter-terrorism raids.

Turnbull opened a summit on Thursday in Canberra of police and intelligence chiefs from around the country on how to deal with the rising threat, highlighting a dramatic drop in the age of suspects.

He urged closer cooperation with Muslim leaders and greater mutual respect across the country.

“The Muslim community are our absolutely necessary partners in this fight against extremism and we need to work very closely with them,” Turnbull said, adding that “the most critically important Australian value in all of this is that of mutual respect.”

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