A man has been charged over a terror plot to attack an Australian army base.
Nayef El Sayed, 25, was one of four people arrested on Tuesday morning after dawn raids on 19 properties in Melbourne as part of a seven-month investigation.
Police say the raids foiled a plan to enter the Holdsworthy Barracks in Sydney and carry out a sustained attack on military staff with semi-automatic weapons.
The men arrested were Australian citizens of Somali and Lebanese descent. Police believe they have links with Al Shabaab, a hardline militant Islamist youth group that is deeply involved in violence in war-torn Somalia.
Mr Sayed appeared in Melbourne Magistrates Court on Tuesday on a charge of conspiracy to commit an act in preparation for a terrorist act.
Three other suspects also appeared in court, but have not been charged. A fifth suspect already in custody on other matters is also being questioned.
Mr El Sayed appeared behind a window and refused to stand for the magistrate. His lawyer told the court Mr El Sayed's religious belief meant he felt he should not stand for any man but God.
Mr El Sayed did not apply for bail and was remanded in custody until October.
About 400 federal and state police in Victoria executed the search warrants about 4.30am local time on Tuesday. Further arrests may be made.
The operation involved officers from the Australian Security Intelligence Organisation, Australian Federal Police, Victoria Police, New South Wales Police and the NSW Crime Commission.
Threats remain, warns Rudd
Officials said Australia's terrorism warning alert would remain at medium level, where it has been since 2003, but Prime Minister Kevin Rudd said the arrests showed that threats remained.
"The sobering element to emerge from today's development is the reminder to all Australians that the threat of terrorism is alive and well," he said in Cairns.
While Australia has never suffered a peacetime attack on home soil, more than 90 Australians have been killed in bomb attacks in Indonesia since 2002.
Mr Rudd said Tuesday's arrests were not linked to deadly bombings at two luxury hotels in Jakarta on 17 July that killed nine people, including three Australians and one New Zealander.
Australia has gradually tightened anti-terrorism laws since the September 11, 2001, attacks on the United States. It has been an active participant in hostilities in Iraq and Afghanistan, where over 1,000 Australians are currently serving with foreign forces.
Security agencies believe the plot was in retaliation for the Australian army's presence in Muslim countries, mainly Iraq and Afghanistan.
The Australian published a report of the investigation before the raids were carried out on Tuesday morning.
Victoria police chief commissioner Simon Overland says this could have jeopardised the operation and an investigation will be carried out into the leak.