Australian authorities have warned that suspected terrorists in Australia are becoming younger, with a 12-year-old now under investigation by security agencies.

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

The Iranian-born Jabar was later shot dead by police.

The Australian Broadcasting Corporation (ABC) reported that the 12-year-old boy was the youngest of 18 suspected extremists named in a court document in March. The boy's name has not been published.

New anti-terror laws

Earlier this week, in the wake of the deadly attack, the Australian government outlined new plans to tighten counterterrorism laws, including restricting the movements of suspects as young as 14. Justice Minister Michael Keenan expressed alarm at the age of children being targeted for radicalization but declined to say how many under the age of 14 were on watch lists.

Federal Police Commissioner Andrew Colvin, meanwhile, confirmed that the threat posed by terrorism had evolved and had become younger. Colvin added that "the problem is getting worse for Australia, not better."

"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," he said.

National concern

On Thursday, Prime Minister Malcolm Turnbull opened a summit 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.

"The shocking murder of Curtis Cheng, a shocking act of terrorism perpetrated by a 15-year-old boy, reminds us yet again that radicalization, extremism can be seen in the very young," he said in his opening remarks.

"This is a real homegrown threat, and it appalls all Australians and it appalls all Muslim Australians," Turnbull added.

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

Growing number of attacks

Canberra has become increasingly concerned about the prospect of lone wolf attacks by individuals inspired by groups such as the self-declared "Islamic State" (IS), and has already cracked down on Australians attempting to travel to conflict zones.

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

The country has been struggling to cope with a string of homegrown terrorism crimes involving teenagers. In September 2014, an 18-year-old was shot dead by police after stabbing two counterterrorism police officers in Melbourne, Australia's second-largest city.

In April, several teens were arrested on suspicion of plotting an IS-inspired attack at a Veterans' Day ceremony in Melbourne. And in May, police arrested a 17-year-old in Melbourne and accused him of plotting to detonate three homemade pipe bombs.

Last December, police forces were faced with a 16-hour siege at a cafe in Sydney, where two of the 17 hostages and the 50-year-old Iranian gunman were killed.

ss/cmk (AFP, AP)