It followed Barack Obama’s request for support in the fight against the extremist militants who are waging a bloody war in Iraq and Syria to establish a hardline Islamic caliphate.
Mr Abbott, the Australian Prime Minister, warned that action in Iraq could be “quite lengthy” and certainly in “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 [Isis] death cult,” he added.
“Isil must be disrupted and degraded at home and abroad, so it is absolutely in Australia's national interests that this mission goes ahead."
“If we could degrade them to the point where they no longer existed, that would be obviously the best possible result,” he said. “It is very difficult to eliminate an idea.”
A poll of almost 7,000 people by the Sydney Morning Heraldfound a narrow margin of support for the intervention among Australians.
About 49 per cent of voters backed air strikes, while 42 per cent were against it and the remainder were unsure.
The news came hours after David Cameron announced that two more British Tornadoes will be deployed in Cyprus to join missions against Isis in Iraq, bringing the total to eight.
The Prime Minister said the additional fighter jets would “keep up the tempo” of air strikes and save lives in Iraq.
Australia’s Air Chief Marshal, Mark Binskin, said the air strikes would start “over the coming days” but did not give specifics.
The intervention was approved by Australia’s National Security Committee following an official request from the Iraqi Government overnight.
Two Australian Air Force planes - an E-7A Wedgetail surveillance and communications jet and a KC-30A refuelling plane - joined operations over Iraq from the al-Minhad Air Base outside Dubai for the first time on Wednesday to support strikes by other nations.
The number of Super Hornets could soon be increased to eight, joining a 200-strong ground force, including special forces, and 400 Air Force personnel from Australia.
Mr Abbott has restricted combat operations and has ruled out Australian troops fighting on the ground.
Australia is one of dozens of countries from Europe, the Middle East and North America that joined the US-led military coalition fighting Isis.