A security analyst says the eldest of three orphaned Australian siblings pleading for repatriation from a Syrian refugee camp has been an Islamic State group propagandist who could potentially face terrorism charges at home.

Australian National University counterterrorism researcher Jacinta Carroll said Wednesday that Zaynab Sharrouf was taken from Sydney to Syria at the age of 13 in 2014 by her extremist parents and became both a victim and supporter of terrorism in a case that was legally and morally complex.

The Australian government has said it is working with the Red Cross to repatriate 17-year-old Zaynab, her two children, her 16-year-old sister and 8-year-old brother from a Syrian camp.

Carroll has discovered that Zaynab became a prominent Islamic State group propagandist making social media posts supporting atrocities.