SYDNEY - A man instructed by the Islamic State to bring down an Etihad Airways flight tried to use an unsuspecting passenger to carry a bomb on board, with a second poison gas plot also in the works, Australian police alleged on Friday.

The improvised device, using "high military-grade explosive", was due to be smuggled onto a July 15 flight from Sydney, but the attempt was aborted before they reached security.

Two men - Khaled Khayat and Mahmoud Khayat -have been charged with terrorism offenses and were refused bail on Friday, with a third still being questioned.