The Australian cabinet has given its approval for fighter jets to join the US-led military action against Islamic State targets in Iraq.
Prime Minister Tony Abbott said IS was a "death cult" that had "declared war on the world" and must be stopped.
IS controls a broad swathe of territory, spanning a borderless stretch of Syria and Iraq.
The US and Arab allies have been bombing IS targets in Iraq and Syria for the past two weeks.
European countries have been attacking only Iraqi sites.
On Thursday, the Turkish parliament backed a motion that could allow its military to enter Iraq and Syria to join the campaign.
IS militants have recently advanced close to the border with Turkey, prompting thousands of Kurdish refugees to cross the border. Turkey is already hosting more than a million Syrian refugees.
The UN says the militant Islamists have committed a "staggering array" of human rights abuses.
In a widely anticipated statement, Mr Abbott said approving military force was "not a decision the government has taken lightly" but that "Iraq should not be alone" in its fight against the militants.
He said the cabinet had also authorised the deployment of special forces to assist and advise the Iraqi military, with the action expected to continue for "months rather than weeks".
"Yes, it is a combat deployment, but it is an essentially humanitarian mission to protect the people of Iraq and ultimately the people of Australia from the murderous rage of the Isil (IS) death cult," he told reporters.
Mr Abbot said there were no immediate plans for Australian involvement to extend to Syria, nor for troops to be involved in combat on the ground.
Canberra has already sent 400 Air Force personnel, 200 special forces members and six warplanes to a US base in the United Arab Emirates.
The decision to join the military action - which did not need parliamentary approval - comes amid growing domestic concern about the number of Australians involved with IS.
The government believes at least 60 Australians are fighting with terror groups in the Middle East and at least 100 are actively supporting them from home.
Last month, police carried out raids on several addresses in Sydney sparked by intelligence reports that Islamist extremists were planning random killings in Australia. The raids, with at least 800 heavily armed officers, led to 15 arrests.
An 18-year-old terror suspect was shot dead last week after he stabbed two police officers in Melbourne. Abdul Numan Haider, originally from Afghanistan, had been summoned to a police station for a counter-terror interview because of concerns over his recent behaviour.
Images have also been published online which appeared to show the young son of an Australian ex-terror convict holding a Syrian's severed head.
Mr Abbott said at the time the image showed "just how barbaric" IS militants were.
(BBC)