In January, police raided 18 locations in southeast Turkey on so-called "intelligence" that fighters linked to al-Qaeda were planning car bomb attacks.
Four alleged fighters and a policeman were then killed in a gunfight, and 17 suspects were arrested.
Al-Qaeda was also blamed for truck bombs that targeted two synagogues in Istanbul on November 15, 2003, as well as the British consulate and a British bank five days later.
The attacks killed at least 63 people, and injured hundreds.
Last year, seven men were jailed for life over the bombings, one of them a Syrian national who was convicted of financing the attacks.