Turkish Airlines, one of the key foreign carriers flying to Iraq, on Friday said it had halted flights to the main city of Iraqi Kurdistan for security reasons amid an offensive by extremist militants.

Turkish Airlines, one of the key foreign carriers flying to Iraq, on Friday said it had halted flights to the main city of Iraqi Kurdistan for security reasons amid an offensive by extremist militants.

"Our flights to Arbil are being cancelled for security reasons until further notice," the airline said in a statement.

Abu Dhabi's Etihad Airways on Thursday announced a suspension of flights to Arbil while Britain has urged citizens living in parts of Kurdistan to leave.

American aircraft earlier bombed positions held by Islamic State insurgents who have advanced to take swathes of northern Iraq.