Australians returning from fighting with terror groups in Syria could still be placed under terrorist control orders in cases where they can't be prosecuted, Malcolm Turnbull says.
The prime minister says foreign fighters returning to Australia following the defeat of Islamic State in Syria and Iraq is a live concern and the government has made a number of changes to security legislation in anticipation.
"We are resolutely remorselessly focused on keeping Australians safe and we pay very close attention to the Australians that may seek to return from the conflict zone in Syria," he told reporters in Sydney on Monday.
About 110 Australians are thought to be overseas fighting with or supporting groups such as IS, with as many as 65 killed.
IS is now facing defeat in Iraq and Syria within the next six months.
It's expected some of those who survive will seek to return home, possibly with plans to commit terror attacks.
Australian Federal Police deputy commissioner Mike Phelan, who's responsible for national security, says the AFP would prefer to prosecute those returning.
"But the practical realities of that are, though, we may not be in a position to prosecute everybody that comes home due to the lack of admissible evidence," he told The Australian.
Mr Turnbull said control orders could be imposed in circumstances where it may be be difficult to prosecute.
Control orders are issued by a court and apply for up to a year. They can be imposed on someone who trained with a terror group or participated in hostilities in a foreign country.
A person subject to a control order may be required to wear a tracking device, report regularly to police and live at a certain location. The order can ban the person from leaving the country, associating or communicating with certain people or accessing the internet.
The government has also introduced legislation to keep convicted terrorists in jail if it's believed they remain a threat.
Mr Turnbull said extensive intelligence sharing was in place with allies and he had discussed stepping up intelligence co-operation during recent meetings at the G20, East Asia Summit and the UN.
"Intelligence is the key and we are working more closely with other like-minded nations, allies, partners, to that end. It is a very, very key priority," he said.
