Car bombers hit Irbil, the capital of Kurdistan in Iraq, killing six members of the security services on Sunday. At least 36 people were reported to be wounded.
Irbil is in a stable part of Iraq and the region has not witnessed such attacks in the past six years.
A central government spokesman said the violence could be linked to fighting between jihadists and Kurd in Syria.
The BBC reports a car bomber rammed a checkpoint leading to a complex housing the interior ministry and a number of security agencies.
Another bomber in an ambulance struck when emergency services arrived. Gunmen on foot also attacked.
TV images showed black smoke rising high above the city and emergency vehicles heading to the scene, which was sealed off by security services.
