Canberra, Nov 15 (IANS): A newly recruited Australian woman intelligence officer had stopped one of the biggest Islamic State inspired terror attacks ahead of Christmas 2016 in Melbourne, a top spy officer said.

The information was revealed only after the Supreme Court of Australia on Wednesday lifted a suppression order on the trials of three men who plotted the attack on iconic Melbourne landmarks, Xinhua news agency reported.

The officer who had then joined the agency only a week back as an analyst, noticed the men "performing in an unusual way", Director General of Australian Security Intelligence Organisation (ASIO) Duncan Lewis said.

"The Christmas crowds were gathering and she noticed this group going to a chemist's shop very late in the night," Lewis said.

"They were in fact picking up the precursors for explosives. That was all the lead we needed."

Prime accused Ibrahim Abbas, pleaded guilty to all charges in February and gave evidence against his brother Hamza Abbas, 23, cousin Abdullah Chaarani, 27, and another Ahmed Mohamed, 25, revealing that they planned to use knives, explosives, vehicles and suicide vests to attack large crowds gathered in the city ahead of Christmas.

All four face lifetime in prison after the court heard that they purchased pre-cursors for explosives as well as machetes as part of their planned attack on Melbourne Central Business District (CBD).

Lewis made the comments during a speech to military officials at the Land Forces conference in Adelaide in September but the information could not be made public until the trial and appeals were concluded.

The four men, all Australia born, were arrested on December 22, two days after they carried out a reconnaissance mission and have been charged with conspiring to carry out a terrorist attack.