Turkey blamed the twin car bombings on May 11, 2013, in the southern border town in Hatay province on pro-Damascus groups.
The Ankara court convicted Nasir Eskiocak over planning and executing the attack, and gave him 53 aggravated life sentences, which carry harsher conditions and replaced the death penalty in Turkey, state news agency Anadolu reported.
Eskiocak was found guilty of killing 53 people including five children and "trying to destroy the country's unity and integrity", the agency added.
The group is a branch of a far-left underground movement founded in 1972, the Turkish People's Liberation Party/Front (THKP/C).
Following the clampdown after the 1980 military coup in Turkey, "Acilciler" went underground and its leader Mihrac Ural sought refuge in neighbouring Syria.
The Turkish foreign ministry in late January sought explanations from Moscow over Ural's presence at the Syrian National Dialogue Congress hosted by Russia in the Black Sea resort of Sochi where representatives of Syrian civil society and politics met.
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