Erdogan and his ministers blamed Bashar al-Assad's secret police, the mukhabarat, for the explosions, which would make this the worst "blowback" the country has suffered for its backing of the Syrian opposition.
It was an orthodox terror attack. The first, smaller bomb detonated outside the town hall. As people came out to see what had happened, a second, much larger car bomb exploded at the busier end of the main street, crowded with shoppers. It sent jets of flame into the air and shattered glass frontages for half a mile around.
Erdogan's policy of "zero problems with the neighbours", pursued actively during the first years of his premiership, has had spectacular consequences.
Many of the leading Syrian rebels are small businessmen who took advantage of easier trade links to travel to Turkey, seeing its prosperity and democracy at first hand and making the money with which they funded their initial arms purchases.
After Assad snubbed Erdogan's earlier pleas to step down, Turkey began backing the rebels, and is now calling for Western intervention.
The authorities said they had arrested nine Turkish citizens from a Marxist group with links to the Syrian mukhabarat. The Foreign Minister Ahmet Davutoglu said the faction behind the bombing was responsible for massacres of Sunnis in two villages near the northern town of Baniyas 10 days ago.
Aytug Atici, an opposition MP for the nearby town of Mersin, said he was worried for the safety of Turkey's ethnic Arab population, many of whom belong to the Alawite sect of Assad's family. Davutoglu blamed the international community for its failure to intervene to end the war. "It's unacceptable for the Syrian and Turkish people to pay the price for this."
