Extreme messages must be opposed: Moriarty

Radical messages posted online to recruit young people to terrorist groups must be challenged, the federal government's counter-terrorism coordinator says.

Greg Moriarty attended a national meeting on Thursday discussing measures to fight homegrown radicalisation in the wake of the fatal shooting of police worker Curtis Cheng in Sydney's west by a 15-year-old gunman.

"The barbaric messages ISIL, Al Qaeda and other groups propagate need to be challenged," Mr Moriarty told reporters in Canberra.

Mr Moriarty said while there were "great partners" in the community who were prepared to dispute extreme messages, law enforcement should be brought in when a person is at risk of radicalisation.

He wants law enforcement agencies to be able to access a wide range of tools to combat terrorism.

"We have to make sure law enforcement does have access when there are worrying signs, when there's a real danger to the community," Mr Moriarty said.

Ideas flagged at the summit would be considered with input from the states and territories.

They would also be discussed at the next COAG meeting in November.

Justice Minister Michael Keenan wants social media to be better targeted to stop the spread of propaganda.

He also flagged more support for families, teachers, peer groups and community leaders to reach out to impressionable youth.

"ISIL is very sophisticated in the way it grooms young people once they've identified somebody who might be vulnerable to their message," Mr Keenan said.