An Australian man sent his unsuspecting brother to Sydney airport to catch an Etihad Airways flight carrying a home-made bomb disguised as a meat-mincer built at the direction of a senior so-called Islamic State commander, police said today.
Detailing one of Australia's "most sophisticated" militant plots, police said two men, who have been charged with terror-related offences, also planned to build a device to release poisonous gas in a public area.
High-grade military explosives used to build the bomb were sent by air cargo from Turkey as part of a plot "inspired and directed" by IS, Australian Federal Police Deputy Commissioner Michael Phelan said.
The plot targeted an Etihad Airways flight on 15 July but the bomb never made it past airport security, he said.
"This is one of the most sophisticated plots that has ever been attempted on Australian soil," Deputy Comm. Phelan said.
Police allege that one of the two men charged late yesterday had been introduced to IS by his brother, who they said was a senior member of the group in Syria.
Communication between the accused man and IS began around April, police said. Under the instruction of the unidentified IS commander, the men built a "fully functioning IED" (improvised explosive device).
One of the brothers was unaware that he was carrying a bomb, disguised as a commercial meat mincer, in his luggage, and tried to check it in at the airport, police said.
"We'll be alleging that the person who was to carry the IED on the plane had no idea they were going to be carrying an IED," Deputy Comm. Phelan said.
Such a device would work like a large grenade, exploding with enough force to blow a hole in an airplane, even if it went off in the cargo hold, said Professor Greg Barton, a security expert at Deakin University in Melbourne.
"I think the logic would be that you pack your explosives in and seal it up, and if someone does a quick physical inspection it just looks like what it is, a meat grinder, because it's not electrical or electronic, it's less likely to be suspicious," said Prof Barton.
Police said there was "a little bit of conjecture" about what happened next, but it appeared one of the accused then left the airport, taking the luggage with him. The man's brother boarded the plane and has not returned to Australia since.
"I want to make it quite clear - it never got near screening. I don't want anyone to suggest that it ... penetrated airport security layers ... because it did not. It didn't go anywhere near it," Deputy Comm. Phelan said.
Etihad said in a statement today it had been working closely with the Australian investigation.
Police arrested four men last weekend in raids across Sydney, Australia's biggest city. One man has been released, while another is still being held without charge under special counter-terror laws.
The two who have been charged are Khaled Khayat and Mahmoud Khayat, who each face two counts of planning a terrorist act. The charges carry a maximum punishment of life in prison.
The men did not apply for bail at a court hearing today, a spokeswoman for New South Wales Courts said, and bail was formally denied. Their next scheduled court appearance is on 14 November.
Police also said they had uncovered the early stages of a plot to build an "improvised chemical dispersion device" designed to release hydrogen sulphide gas. Precursor chemicals and other components were found but the accused were "a long way" from making a functioning device.
Foul-smelling hydrogen sulphide, or "rotten egg gas", is deadly in high concentrations.
Police said "preliminary and hypothetical" discussions between the accused and IS suggested a plan to deploy it in a crowded place, such as public transport.
Australia, a staunch US ally that has sent troops to Afghanistan and Iraq, has been on heightened alert since 2014 for attacks by home-grown militants returning from fighting in the Middle East, or their supporters.
