A government minister said security services are also hunting for two men who trained in a Libyan jihadist camp with the Sousse attacker, 23-year-old student Seifeddine Rezgui.
Thirty-eight people, including three Irish tourists, were killed when Rezgui opened fire in the resort last Friday.
Charlie Flanagan, Irish Minister for Foreign Affairs and Trade, told BBC Evening Extra that he understands the bodies of the Irish citizens will arrive in Dublin today.
The three Irish victims are Lorna Carty, from County Meath, and County Westmeath couple Martina and Laurence Hayes.