Turkish state media say police have detained 14 suspected al-Qaida militants in a series of raids across western Turkey.
The Anatolia news agency said the suspects were planning to attack the U.S. embassy in Ankara and other unspecified targets.
It reported police captured the suspects and seized explosives and weapons in Ankara and in the cities of Bursa and Yalova in operations on Monday and Tuesday. The seized items included 700 kilograms of chemicals used in bomb-making.
Al-Qaida militants carried out a series of bomb attacks in Istanbul in 2003, killing almost 60 people.