Rescue teams arrive at the scene after an explosion outside a courthouse in Izmir, Turkey, January 5, 2017. [Photo/Agencies]

Ayyildiz said the clash outside Izmir's main Bayrakli courthouse erupted after police officers tried to stop a vehicle at a checkpoint and that the attackers detonated the car bomb while trying to escape.

The PKK and its affiliates have been carrying out increasingly deadly attacks over the past year and a half, ever further from the largely Kurdish southeast, where they have fought an insurgency for more than three decades.

A PKK offshoot claimed responsibility for twin bombings that killed 44 people, most of them police officers, and wounded more than 150 outside an Istanbul soccer stadium on Dec. 10.

A car bomb a week later killed 13 soldiers and wounded 56 when it tore through a bus carrying off-duty military personnel in the central city of Kayseri, in an attack President Tayyip Erdogan also blamed on Kurdish militants.

There was no immediate claim of responsibility for the attack in Izmir, a liberal coastal city which had largely escaped the violence that has plagued Istanbul and the capital Ankara in recent months.

Police detained 20 suspected Islamic State militants thought to be of Central Asian and North African origin in Izmir on Wednesday, in raids Turkish media said were linked to the Istanbul nightclub attack.