Police have about 70 terrorism investigations going on across the country, as ASIO signals concern that some children of foreign fighters may pose a jihadism risk if they return home.

Police and intelligence officials used a hearing of a terrorism legislation watchdog on Friday to make the case for measures such as bail-like control orders, and for declared no-go zones in Syria and Iraq to remain in place.

Australian Federal Police Deputy Commissioner Mike Phelan says police are investigating around 70 terrorism cases. Credit:Alex Ellinghausen

The Australian Federal Police's deputy commissioner for national security, Mike Phelan, told the Independent National Security Legislation Monitor, James Renwick, that it had "70-odd investigations" under way into terrorism cases.

The number is significant because it shows how many potential plots are sufficiently advanced for police to be gathering evidence with a view to launching prosecutions. It would include cases such as terrorism fundraising as well as possible attack plots, and also includes cases that are already before the courts.