WASHINGTON (REUTERS) - The US Federal Aviation Administration (FAA) has barred all American airlines from flying over Syria, saying the ongoing armed conflict and volatile security environment poses a "serious potential threat" to civil aircraft.

"Due to the presence of anti-aircraft weapons among the extremist groups and ongoing fighting in various locations throughout Syria, there is a continuing significant potential threat to civil aviation operating in Syrian airspace," the agency said in a statement.

The FAA previously had issued a notice that advised all American carriers to avoid flying over Syria. The new rule requires carriers to contact the FAA before operating in the airspace.