The PST security service said the three suspects are Norwegian citizens aged 29, 27 and 24. The oldest was born in Somalia and the other two were born in the former Yugoslavia. PST said two of the suspects have been fighting for the jihadist group Islamic State of Iraq and the Levant, which is fighting in Syria.
The agency said the three were arrested "to prevent additional support or adherence to ISIL," which is considered as a terrorist organisation under Norwegian law.