Two suspected Kurdish militants, a police officer and a court worker have been killed in an explosion and gun battle in western Turkey.
Officials said the attackers clashed with police and set off a car bomb after their vehicle was stopped at a checkpoint outside the main courthouse in Izmir, Turkey’s third-largest city.
The attack highlighted the country’s deteriorating security five days after a gunman killed 39 people in a New Year’s Day mass shooting at an Istanbul nightclub.
Deputy Prime Minister Veysi Kaynak said a much larger attack was apparently being planned, based on the weapons found at the scene in Izmir, which is located on the Aegean coast.
The local governor said the arms included Kalashnikov rifles, hand grenades and ammunition for rocket-propelled grenade launchers.
“Based on the preparation, the weapons, the bombs and ammunition seized, it is understood that a big atrocity was being planned,” Mr Kaynak told reporters.
CCTV of the Izmir bombing
Izmir police shot dead two of the attackers and were hunting a third, a police source and the state-run Anadolu agency said.
Two people, believed to have sold the vehicle used in the attack to the assailants, were subsequently detained, security sources said.
Initial findings suggested that Kurdistan Workers Party (PKK) militants were behind the attack, Izmir Governor Erol Ayyildiz said.
He said a second vehicle had been detonated in a controlled explosion.
Anadolu said police suspected the attackers had planned to escape in this vehicle.
NATO member Turkey is part of the US-led coalition fighting Islamic State in Syria and is also battling an insurgency by the PKK in the largely Kurdish south-east.
It regularly bombs PKK camps in northern Iraq, and its military operations in Syria also aim to stop Kurdish militias it sees as an extension of the PKK from gaining territory there.
“Turkey will be instrumental in its region. These [attacks] will never prevent us from being present in areas like Iraq and Syria, which produce terrorists like viruses,” Mr Kaynak said.
The bombing came after police detained 20 suspected IS militants in Izmir on Wednesday, in raids Turkish media said were linked to the nightclub attack. The gunman is still at large.