A Turkish police officer and a court employee were killed when the car bomb exploded in front of the Izmir courthouse on Thursday afternoon, officials said.

Police at the scene shot dead two suspected attackers in a firefight immediately after the blast, a security source told Reuters. A third assailant is believed to be on the run.

Provincial governor Erol Ayyildiz said the clash erupted after police tried to stop a vehicle at a checkpoint near the courthouse.

"Terrorists detonated the car bomb while trying to escape," he told reporters, adding that initial findings suggested the Kurdish PKK militant group was responsible. He said police seized an automatic rifle, a rocket launcher and eight hand grenades from the attackers.

'Bigger attack planned'

Deputy Prime Minister Veysi Kaynak said the weapons suggested the militants had planned a much larger attack.

"Based on the preparation, the weapons, the bombs and ammunition seized, it is understood that a big atrocity was being planned," he told reporters.

Television footage from the scene showed several ambulances outside the building, as well as flames and plumes of smoke. At least 10 people were taken to hospital.

Spike in violence

NATO member Turkey has been rattled by a string of recent attacks claimed mainly by the "Islamic State" (IS) extremist group or Kurdish militants. 

Thursday's explosion comes less than a week after a gunman shot dead 39 people at an Istanbul nightclub in the early hours of New Year's Day. That attack was claimed by "IS."

There was no immediate claim of responsibility for the attack in Izmir, a liberal coastal city that had largely been spared the violence seen in major cities like Ankara and Istanbul.

Turkish officials have blamed the PKK, considered a terrorist organization by Turkey, the US and the EU. The group is currently fighting an insurgency in southeastern Turkey, where it has carried out a number of deadly attacks over the past 18 months. 

nm/se (AFP, Reuters, AP, dpa)