The foreign minister has hosed down concerns a group of suspected jihadists who fought in the Middle East and returned to Australia could escape prosecution because of a legal loophole.
News Corp Australia reports say up to 20 are back in the country and wandering free in the community.
Federal parliament passed counter-terrorism laws in October prohibiting travel to terrorist hot spots without a valid excuse, such as aid work or journalism.
But there are fears those who returned before the bans were introduced might escape censure.
Julie Bishop has declined to comment on specific cases, but maintained returned fighters can still be investigated and monitored.
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"If we have the evidence they have been engaged in these activities they can still be investigated," Ms Bishop told Fairfax radio.
"They can still be persons of interest to our security agencies."
She acknowledged it was difficult to gather evidence of people's activities in Syria and Iraq because those were hostile environments.
"It's hard to get eyewitness accounts of people working with terrorist organisations overseas but we're doing all we can to ensure that those people ... who are security risks are thwarted," she told Sky News.
"We know from experience that once people become battle-hardened, experienced terrorists overseas, they could well come back here to try and carry out some sort of terrorist activity in their own country."
