"Thirteen people were arrested and brought before a court," said Governor Erdal Ata in a televised statement.

The car bomb attack on August 20 killed nine people, four of them children, and wounded dozens in Gaziantep, causing nationwide fury and panic.

Police are still searching for a key suspect, identified as Murat Filiz, who is believed to be a member of the rebel Kurdistan Workers' Party (PKK).

Turkish officials blamed the PKK for the bombing, but the rebels, who have been fighting for autonomy in Turkey's southeast since 1984, did not claim responsibility for the attack.

The targeting of Gaziantep -- a city previously spared the violence wrought by PKK rebels, and which lies just 50 kilometres from the Syrian border -- has raised suspicions that Syrian President Bashar al-Assad's regime could have had a hand in the attack.

Some government officials believe the Syrian regime -- a one-time ally of Turkey -- is helping PKK rebels in revenge for Turkey's support for anti-Assad rebels.

Ata said Friday that the theory could not be proved.

Turkey is sheltering more than 70,000 Syrian refugees in camps in the south of the country, and also providing sanctuary to Syrian military defectors.

The conflict with the PKK, which is considered a terrorist organisation by Turkey and much of the international community, has claimed some 45,000 lives over nearly three decades.

Just two days after the car bombing, further violence in Turkey's south-east between soldiers and Kurdish rebels left 21 people dead.