Australia charges two men in Sydney over plot to blow up plane

One man is being held without charge under special terror-related powers

Australian Federal Police officers stand near the check-in counters at the Sydney Airport Domestic terminal in Australia (REUTERS/David Gray)

Two men have been charged with terrorism offences in Sydney for their alleged plot to blow up a passenger plane.

A 49-year-old man and a 32-year-old man have been charged with two counts of acts in preparation for, or planning, a terrorist act, the Australian Federal Police said.

Both men are scheduled to appear at a court in the Sydney suburb of Parramatta on Friday morning, the AFP said.

They both face life imprisonment.

The plot spurred Australia's intelligence agency to raise the aviation threat level to "probable," prompting tighter airport security measures, before the risk was downgraded to "possible".

A 50-year-old man was released from custody without charge, while one man is being held without charge under special terror-related powers.

The charges come as it emerged the plot was narrowly thwarted at Sydney Airport, after the suitcase containing the improvised device was found to be too heavy to be checked in.

Australian media report the device was a meat mincer designed to explode or disperse deadly gas on an Etihad flight from Sydney to the Persian Gulf.

The aviation threat level was downgraded to "possible", Prime Minister Malcolm Turnbull told a news conference in Perth on Thursday, since the plot had been disrupted and contained.

Abu Dhabi's Etihad Airways has said it is assisting Australian federal police in the investigation.

Since 2014, Australia has been on heightened alert for attacks by home-grown militants returning from fighting in the Middle East, or their supporters.

Although the country has suffered few domestic attacks, authorities say 13 significant plots have been foiled in that time.

The 2014 Lindt cafe siege in Sydney, in which the hostage-taker and two people were killed, was Australia's most deadly violence inspired by Isis militants.