I think it's weird that the bombings haven't been claimed by one group or another. ISIS would make sense if this was an standalone operation such as those that happened in Europe (lone men mostly working by themselves and losely affiliated with ISIS groups).
The Kurds have little interest on antagonizing public opinion... Which could be a reason not to claim the bombing for themselves even if it was some kurd related agent who did it. I heavily doubt this is the case, but who knows.
Pretty much makes it clear that it was turkeys who staged the attack. Turkey is trying to build up resentment towards its most hated enemy.....the Ham.