Two men have been charged with planning a terrorist act after police uncovered an alleged Sydney-based plot to bring down a plane.

A 49-year-old and a 32-year-old, both from south-west Sydney, have each been charged with two counts of acting in preparation for or planning a terrorist act, Australian Federal Police said in a statement on Thursday night.

Both men are scheduled to appear in Parramatta court on Friday morning.

Four men were arrested on Saturday night when armed counter-terrorism officers raided four properties in Surry Hills, Lakemba, Wiley Park and Punchbowl over the alleged plot.

One man was released on Tuesday without charge; another man, who was arrested in Surry Hills, remains in police custody.

The prime minister, Malcolm Turnbull, also spoke before the charges were brought. “Investigations have proceeded very well in terms of uncovering evidence,” he told reporters in Perth. “The police have uncovered very substantial evidence.”

The New South Wales (NSW) police commissioner Mick Fuller defended the “outstanding job” done by his officers following criticism from 50-year-old Abdul Merhi, who was arrested on Saturday but released without charge.

Merhi’s lawyer, Moustafa Kheir, said he would review “what basis police had to do what they did” and said his client’s life had been “turned upside down”.

Fuller said he welcomed the scrutiny, and that he had a responsibility to protect the people of NSW. “We mobilised quickly and really from my perspective we stopped what could have been a terrible crime,” he said.

Australian airports ramped up security procedures after the weekend raids. However most arrangements have now returned to normal after the aviation terror threat level was lowered to “possible” on advice from Australia’s spy agency, Asio.



The threat level was raised to “probable” when the plot was discovered.

“Travellers will see progressive adjustments to airport security over the next 24 hours,” Turnbull said in a statement on Thursday. “This includes a return to normal arrival times at airports for check-in as advised by your airline.”

Australian Associated Press contributed to this report