British newspaper The Times alleges that the men were among a number of foreign fighters swapped for 46 Turks who were taken prisoner from their country's consulate in Mosul, Iraq, in June and released last month.
The newspaper claims the list also includes two British citizens, two Swedish nationals, two Macedonians, one Swiss national and one Belgian.
Other Isis fighters involved in the swap are understood to have been taken to Turkish hospitals or kept in Turkish prisons. Others are understood to have been released and taken in by Syrian rebel groups.
The release of the Turkish hostages hit the headlines at the end of September. There were 49 in total – 46 Turkish citizens and three Iraqis – and included the Turkish consul, diplomats, special forces police and children.
Security experts have suggested that the Turks were key "bargaining chip" for Isis.