Gunman reportedly claims to be ISIL after killing one and wounding three police officers in attack.

Australian police are treating a deadly siege in the southern city of Melbourne as an “act of terrorism” after a claim by the Islamic State of Iraq and the Levant (ISIL, known as ISIS) group that one of its fighters was the gunman responsible.

Police shot dead Yacqub Khayre on Monday after he held a woman hostage inside an apartment building in Melbourne, Australia‘s second-largest city.

Police confirmed on Tuesday that Khayre, who was acquitted of a plot to attack a Sydney army base in 2009, had shot a man dead in the foyer of the building.

“This terrorist attack by a known criminal, a man who was only recently released on parole, is a shocking, cowardly crime,” Prime Minister Malcolm Turnbull told reporters in the capital, Canberra.

“It is a terrorist attack and it underlines the need for us to be constantly vigilant, never to be deterred, always defiant, in the face of Islamist terrorism,” he said.

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Victoria state Police Commissioner Graham Ashton said police were still investigating after ISIL claimed responsibility for the attack via its Amaq news agency.

“We’re aware of them having claimed responsibility, but then they always tend to jump up and claim responsibility every time something happens, so we note that that has happened,” Ashton said.

After holding the woman hostage for several hours, Khayre burst out of the building firing at police, who shot back and killed him. The woman was rescued unhurt, but three police officers suffered non-life threatening gunshot wounds.

Amaq said the attack was launched because of Australia’s membership in a US-led coalition fighting against the armed group in Syria and Iraq.

Police were also investigating a telephone call made to the newsroom of Australian TV broadcaster Seven Network during the siege.

The network said it received a phone call Monday afternoon from a distressed woman who said she was involved in a hostage situation.

“We asked her more information, at that point a man came on the same line and said ‘This is for IS, this is for al-Qaeda,'” Seven news director Simon Pristel said.

“We asked for more information and that’s when he hung up,” Pristel added.

Ashton said Khayre, an 29-year-old Australian of Somali heritage, had a long criminal history and was on parole at the time of the attack.