In pre-dawn raids, some 400 officers from the Australian Federal Police, Victoria Police and NSW Police launched a series of raids in Melbourne under operation codenamed 'Operation Neath' and arrested four people - all Australian citizens. Some plotters were of Somali descent and others Lebanese.
Police said those who were arrested are being questioned and several others are assisting with inquiries.
The raids followed a seven-month surveillance against the plotters, who are allegedly linked to al-Shabaab, a Somali Islamic extremist group, Australian Federal Police Acting Commissioner Tony Negus told reporters.
A NSW police spokesperson said 20 officers from the Counter Terrorism and Special Tactics Command helped in theMelbourne phase of the investigation over a number of months.
"Details of the planning indicate the alleged offenders were prepared to complete a sustained attack on military personnel until they themselves were killed," a federal police spokesman said.