Four more people have been held over the two car bomb attacks that killed dozens in a Turkish town near the Syrian border, bringing the number of suspects in custody to 13.
Police were still searching for six other wanted suspects, Interior Minister Muammer Guler said. Turkish authorities have blamed the attack on a Marxist group with alleged links to the Syrian intelligence agency, but have not named the group.
Turkish Prime Minister Recep Tayyip Erdogan said the death toll stood at 51 people, including five Syrians.
Saturday's powerful bombings were the deadliest in Turkey in years, shattering the border town of Reyhanli, a main hub for Syrian refugees and rebels fighting against Syrian President Bashar Assad's regime.
A statement carried by Syrian state television following a cabinet meeting in Damascus put the blame on Turkey and its support for the rebels. Accusing the Syrian state of these cowardly and terrorist acts is totally baseless," it said.
It added: "The Turkish government is responsible for the situation in the border areas through turning them into a haven and passage for the terrorists and allowing gunmen to use the Turkish lands to commit crimes against the Syrians."
Once a close ally of Syria, Turkey has turned into one of the Assad regime's harshest critics. It is a key supporter of the Syrian rebels, offering shelter for many senior and lower-ranking defected Syrian soldiers.
Mr Erdogan, who previously rejected the Syrian denial of involvement as a lie, dismissed the offer of a joint investigation. "At the moment, there isn't a legitimate administration accepted by the Syrian people," he said. "There isn't (an administration) we can conduct any joint work with... How can we accept an administration that is not accepted by the people?"
Authorities are looking for more suspects, including four people who may have been involved in planning the attack and two people suspected of helping the attackers.
The bombings have sparked speculation that Turkey would be drawn into its neighbour's civil war, but Mr Erdogan reiterated that Turkey would act with restraint.