Turkey Reports Airstrike on Iraq - New York Times: "ANKARA, Turkey (AP) -- Turkish jet fighters bombed Kurdish rebel targets in northern Iraq early Sunday, Turkey's military said, marking an escalation of force against the outlawed separatist group. An Iraqi official said the planes attacked several villages, killing one woman."
This is interesting because the US would have had to have allowed it. The US maintains a Combat Air Patrol (CAP) over Iraq. We have good to excellent radar coverage extending well beyond Iraq's borders. The only reason I can see that the CAP didn't drop the Turkish aircraft is that they were told not to.
The Kurdish Workers Party (PKK) is a terrorist organization. The best solution is for the Kurds in Northern Iraq to police the PKK themselves. If they're not going to do that then they're going to keep giving Turkey an excuse to come over the border and handle the problem their own way.
EDIT: BBC quotes a Turkish General as saying the US gave advance approval.