Istanbul: A bomb exploded on Sunday outside police headquarters in the southeastern Turkish city of Gaziantep close to the Syrian border, killing one policeman and wounding 13 other people, the local governor said.

Gaziantep regional governor Ali Yerlikaya was quoted by Turkish media as saying nine of those wounded were police. NTV television said the explosion was caused by a car bomb and had been followed by sounds of gunfire.

Television pictures showed chaotic scenes outside the imposing police headquarters in Gaziantep as ambulances rushed to help wounded lying on the ground.

One of the main cities of Turkey’s southeast, Gaziantep has a population of around 1.5 million and is also a major hub for refugees who have fled the war in neighbouring Syria.

The attack comes with Turkey on edge after two deadly attacks in Istanbul this year blamed on terrorists and a pair of attacks in Ankara that were claimed by Kurdish militants and killed dozens.

However, there was no immediate indication over who could have carried out the attack in Gaziantep.

Police security has been stepped up across the country on Sunday as Turkish leftist and labour activists prepare to celebrate May Day, an event that often ends in clashes with security forces.