BAGHDAD, July 12 (Reuters) - Iraq's southern shrine city of Najaf declared a rare curfew on Thursday after discovering a possible security threat, a city official said. Intelligence sources had revealed the presence of several suspected militants in the city, prompting a widespread clampdown, the official in the department of information said on condition of anonymity. The curfew would be imposed from 1800 GMT until further notice, he said. Najaf, home to the Imam Ali mosque revered by Shi'ites, is relatively calm compared with other parts of Iraq but has been targeted by Sunni Islamist al Qaeda militants before. In 2003, a car bomb outside the Imam Ali mosque during prayers killed at least 83, including top Shi'ite Muslim leader Ayatollah Mohammed Baqer al-Hakim.
