The suspects were rounded up in simultaneous raids in Istanbul and the northeastern province of Tekirdag, the private Dogan news agency reported. It did not cite a source for the report. Interior Ministry officials and police in Istanbul and Tekirdag refused comment on the report which came on the eve of U.S. Secretary of State John Kerry's visit to the Turkish capital, Ankara.
Police raided nine houses in Tekirdag and two others in Istanbul and found diagrams and photographs of the U.S. Consulate, a synagogue and a church in Istanbul, according to the Dogan report.
Homegrown militants tied to al-Qaida carried out suicide attacks on the British Consulate, a British bank and two synagogues in Istanbul in 2003, killing 58 people.
In 2008, an attack blamed on al-Qaida-affiliated militants outside the U.S. Consulate in Istanbul left three assailants and three policemen dead.
The U.S. Embassy in Ankara was the target of a suicide attack earlier this month. A Turkish security guard was killed in the attack, which was claimed by a domestic militant leftist group opposed to U.S. policies in the Middle East.