Three men alleged to have plotted a suicide shoot-out at an Australian army base have been charged and will appear in court later today.
About 400 police swooped on 19 properties in Melbourne's north, the inner city and southwestern Victoria about 4.30am (AEST) on Tuesday.
One man, Nayef El Sayed, 25, of Glenroy, appeared in the Melbourne Magistrates' Court the same day, charged with conspiring to do acts in preparation for an armed attack on the army base at Holsworthy, in Sydney's west.
Sayed did not apply for bail and was remanded in custody to reappear in court in late October.
Three other men — Saney Edow Aweyz, Abdirahman Ahmed and Yacqub Khayre — also appeared in court on Tuesday but were not charged until Wednesday morning with the same offence as Sayed.
Australian Federal Police (AFP) Acting Chief Commissioner Tony Negus said the men were allegedly planning a suicide shoot-out with automatic weapons.
"The men's intention was to actually go into the army barracks and to kill as many soldiers as they could before themselves, they were killed," Mr Negus told a packed media conference on Tuesday.
"Potentially this would have been, if it had been able to be carried out, the most serious terrorist attack on Australian soil."
He said investigators also believed the men had links to a north African terrorist group, al-Shabaab, which has links to al-Qaeda.
Following a seven-month joint operation, 400 AFP and Victoria Police officers launched raids at 4.30am (AEST) on Tuesday on properties in suburbs in Melbourne's north, inner city Carlton and Colac in the state's southwest.
The four arrested men are Australian citizens of Lebanese or Somalian descent.
Police are also interviewing a fifth man, a 33-year-old, who is already in custody in relation to other matters.
El Sayed, meanwhile, defiantly refused to stand when asked by Magistrate Peter Reardon in court on Tuesday.
El Sayed, 25, told Mr Reardon through his lawyer he stood for no man, only his own God.
Following the filing hearing, the big, bearded man, who sat between two security guards behind glass, was remanded in custody to reappear in court in October.
AFP agent David Kinton earlier told the court police believed there was a conspiracy to commit an act in preparation for terrorism.
He said there were a number of phone intercepts in which another suspect, Saney Aweyz, allegedly raised the possibility of sending men to be involved in the civil war in Somalia.
He said police had also recorded other discussions about engaging in violent activity in Australia.
Mr Kinton said text messages seized by police involving other people discussed the address of a military base in Sydney and the name of a train station.
Intercepted phone calls also revealed discussions about attempts to find an Islamic religious figure who would support a violent attack in Australia, he said.
A 35-year-old man from Lakemba, in Sydney's southwest, was assisting police with their inquiries into the alleged plot.
The counter-terrorism operation, dubbed Operation Neath, involved officers from the Australian Security Intelligence Organisation, the AFP, Victoria Police, NSW Police and the NSW Crime Commission.