Australian police shot dead a teenager after he stabbed two counter terrorism officers, days after sweeping raids involving hundreds of police thwarted what they said was an imminent plot to behead a member of the public.
Australia, a staunch ally of the United States and its escalating action against the Islamic State in Syria and Iraq, is on high alert for attacks by home-grown militants returning from fighting in the Middle East.
Security has been tightened at public places, including Parliament House in Canberra where police are armed with assault rifles, and at major sports events.
The 18-year-old man, who had his passport suspended a week ago, was asked to attend a police station in the southern state of Victoria on Tuesday night because his behavior was "causing concern", police said.
"This was a planned and agreed meeting that was to occur at the Endeavour Hills police station. When these two police officers approached him, they were stabbed, one very seriously," Victoria Police Chief Commissioner Ken Lay told reporters on Wednesday.
"One of the injured police discharged his firearm, fatally wounding the 18-year-old."
Police said the man had been displaying a flag linked to the militant group the Islamic State at a local shopping mall and had been "of interest" to police for months. Local media reported he was of Afghan origin and that he had been shouting insults about Prime Minister Tony Abbott and the government before he was shot.
"I can advise that the person in question was a known terror suspect who was a person of interest to law enforcement and intelligence agencies," Justice Minister Michael Keenan told reporters on Wednesday.