It appears Saturday's twin bombings in the Hatay province border town of Reyhanli were orchestrated by a Turkish group linked to the Syrian regime, Erdogan said.
Five of the suspects are members of the terrorist Revolutionary People's Liberation Party/Front while the remaining four are members of Acilciler, a splinter faction of the Turkish People's Liberation Party/Front.
"Both Turkey and Reyhanli will overcome this incident with ease," Erdogan told a parliamentary group meeting, adding that terrorist acts are intended to destabilize society.
Many Turkish government officials blame the bombings on a group linked to Syria.
Interior Minister Muammer Guler told reporters the bombings were carried out by "an organization in close contact to pro-regime groups in Syria."