Malcolm Turnbull says an increase in the number and severity of terrorist attacks across the world demands new tools to keep Australians safe.

"The threat is real," the Prime Minister said yesterday in Sydney, unveiling two new tranches of anti-terrorism legislation.

"We can never ever be complacent and we are not; we are focused constantly on the single most important obligation of our Government ... which is to preserve and protect the safety of the people." Turnbull will work with the state and territory leaders to roll out a system of post-sentence preventative detention for terrorists who are at high risk of reoffending.

The process will be overseen by the courts and informed by detailed medical and psychological checks.

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The Prime Minister also revealed that the Government would adopt the recommendations of a committee which looked at the previous tranche of anti-terrorism legislation and this would be put to Parliament as soon as possible.

The bill, which was introduced late last year, extends control orders to juveniles to the age of 14, down from 16 years of age. It will also introduce a new offence of advocacy of genocide.

Attorney-General George Brandis said juveniles were in a different position to adults even though they were potentially just as dangerous.

Brandis will meet with state and territory attorneys-general in coming days to discuss the new laws.

The preventative detention change would match similar laws already in place for sex offenders and violent criminals in some states and comes after leaders agreed to the scheme at the meeting of the Council of Australian Government in Canberra in April.

Brandis said the change would be reviewed on a periodic basis.

"But I make no apology for the Government taking the view that if a person, having served a sentence of imprisonment for a serious crime, shows every indication of a willingness to repeat that crime, to reoffend as soon as they are released, they should remain behind bars," he told ABC radio.

He refused to comment on whether there were terrorists in jail now that would be kept behind bars as a result of the proposed laws, and said he was "reasonably confident" of the laws surviving a High Court challenge.

- AAP