(ANSA) - BELGRADE, 05 NOV - Three aircraft were targeted with bomb threats in Bulgaria, prompting security measures at Sofia and Plovdiv airports. Bulgarian media reported this, citing the Ministry of Interior. Two flights from Copenhagen and Madrid arrived at Sofia's Vasil Levski Airport, and authorities have begun screening passengers and crew. A third flight from London landed in Plovdiv. At the moment, no dangerous items have been reported on board the aircraft. The authorities are conducting investigations to determine the source of the threats. Security measures at airports have been strengthened. (ANSA).