8:34am:
Live: Prime Minister Tony Abbott speaks
Prime Minister Tony Abbott has just emerged from a meeting of cabinet's National Security Committee and is delivering a statement to the press at Parliament House in Canberra, reports Bevan Shields.
"Early this morning the Martin Place siege ended with the death of the lone gunman and, tragically, the loss of two hostages, innocent Australians caught up in the horror of yesterday," Mr Abbott said.
"Five other people, four hostages and a NSW police officer, have been injured.
"State and Commonwealth agencies are investigating. Understandably, there is lot of speculation but it will take time to clarify exactly what happened in Martin Place and why. What we do know is that the perpetrator was well known to State and Commonwealth authorities. He had a long history of violent crime, infatuation with extremism and mental instability.
"We know that he sent offensive letters to the families of Australian soldiers killed in Afghanistan and was found guilty of offences related to this. We also know that he posted graphic extremist material online."
"As the siege unfolded yesterday, he sought to cloak his actions with the symbolism of the ISIL death cult. Tragically, there are people in our community ready to engage in politically motivated violence."
Mr Abbott was due to fly back to Sydney yesterday but cancelled the flight to remain in Canberra to monitor the situation.
Mr Abbott will not take questions during this press conference.