Turkish police earlier this year uncovered what they claim to be a plot linked to al Qaeda to bomb a synagogue in Istanbul and the U.S. embassy in Ankara.
Twelve people were arrested during a raid in February on two houses in Istanbul and Corlu in February, the New York Times reported on Thursday, quoting Turkish media.
Eight of them were Turks, two were Chechens and two were Azeris.
Turkish police seized nearly 50 pounds of plastic explosives with detonation systems, six laptops and other evidence during a raid on two terrorist cells, one in Istanbul and one in Çorlu, in the province of Tekirdağ on the Sea of Marmara.
Documents found on the computers, including photographs and floor plans, revealed preparations for bomb attacks on a synagogue in the Balat district of Istanbul, the U.S. embassy and the Rahmi M. Koc Museum.
Turkish police said it was tracking an al-Qaeda man who arrived in the city of Tekirdağ two years ago after receiving military training in Afghanistan. The surveillance led to the February raid.
In February, a Turkish leftist group bombed the U.S. Embassy in Ankara, killing a Turkish security guard. The attacker blew himself up inside U.S. property, blowing the door off a side entrance and sending smoke and debris flying into the street.
In November 2003, car bombings in Istanbul shattered two synagogues, killing 30 people and wounding 146. Authorities said the attack was characteristic of al-Qaeda.