Case follows repatriation of women and children held for years in Syrian camps without trial.
Australian Federal Police have not made any arrests but say inquiries are ongoing.
Those arrested reportedly took part in what officials described as 'terrorist attacks' in Turkiye.
Nigerian Army lauds joint US operation as part of ongoing military campaign to 'hunt down and kill terrorists anywhere'.
Attacks conducted days after US and Nigeria say they killed deputy ISIL leader.
Nigeria and the US say 'key' ISIL leader was killed in joint military operation in Borno state.