The bombings marked the biggest incident of cross-border violence since the start of Syria's bloody civil war and have raised fear of Turkey being pulled deeper into the conflict.
Harsh accusations from both sides signaled a sharp escalation of already high tensions between the two former allies.
"This incident was carried out by an organization which is in close contact to pro-regime groups in Syria and I say this very clearly, with the Syrian mukhabarat," said Interior Minister Muammer Guler.
"We have determined that some of them were involved in the planning, in the exploration and in the hiding of the vehicles," he said.
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Yesterday's twin bombings fifteen minutes apart in the Turkish town of Reyhanli, a hub for Syrian refugees and rebels close to Syria, also wounded dozens of people, including 50 who remained hospitalised today.
Guler said authorities had so far identified 35 people who died in the attack and three of them were Syrians.
Turkish authorities determined that the nine were involved through their "testimonies and confessions," according to Deputy Prime Minister Besir Atalay. He did not elaborate.
"Syria didn't and will never undertake such acts because our values don't allow us to do this," al-Zoubi told a news conference.
He accused Turkey of destabilizing the border areas between the two countries.
"The Turkish government had turned the border areas into centers of international terrorism, as it is still facilitating the arrival of arms and explosives, improvised explosive devices, cars, money and murderers to Syria," he said.
Turkey has firmly sided with the Syrian opposition since the uprising against Assad's regime erupted in March 2011, hosting its leaders along with rebel commanders and providing refuge to hundreds of thousands of Syrian refugees.