Captagon has been sweeping the Middle East for years, with large seizures reported weekly, particularly in the oil-rich Gulf Arab states which are its biggest market.

The Federal Intelligence and Investigation Agency said the microlight entered Iraqi airspace from neighbouring Iran on Friday.

It said agents were alerted to the flight by a tip-off and opened fire on the aircraft.

"That forced the pilot to land. He fled towards the border of a neighbouring country," the agency said in a statement.

The statement said the million captagon pills recovered in a search of the abandoned aircraft were intended for sale inside Iraq.

But a senior security forces officer told AFP the microlight "came from Iran" and was "headed for Kuwait" with its consignment of the highly addictive drug.