Prime Minister Tony Abbott has described the mission to Iraq as “right, just and necessary” for the protection of Australians and Iraqis.

Australia’s military mission to Iraq is right, just and necessary.

That was the message Prime Minister Tony Abbott delivered to Australian Defence Force personnel as they prepared to head to the Middle East on Thursday.

The government has yet to commit to a specific task in Iraq, pending consultation with the Iraq government, the United States and other allies.

Mr Abbott says it is essentially a humanitarian mission to disrupt and degrade the operations of Islamic State, also known as ISIL, and in so doing protect the people of Iraq and Australia.

“They hate our freedom, our tolerance, our democracy,” he told personnel before they flew from RAAF Base Williamtown near Newcastle on Thursday.

“You are there to protect us. You are the long, strong arm of Australia.

“What you are doing is right, it’s just and it’s necessary.”

Mr Abbott’s speech came after more than 800 federal and state police in Brisbane and Sydney foiled an alleged plot involving Australians linked to Islamic State to undertake a public execution in Australia.

He said any combat operations would be limited to air strikes by Super Hornets, and special forces would provide training and advice to Iraqi and Kurdish forces.

Australian Defence Force chief Mark Binskin endorsed the notion of not calling the mission another Iraq “war”.

“War would give them a legitimacy that they don’t deserve,” Air Chief Marshal Mark Binskin said.

“I do see this as a counter-terrorist operation.

“What we’re looking to be able to do is disrupt and degrade ISIL and take away their viability on the battlefield.”

Air Chief Marshal Binskin said Islamic State’s action against minority groups was brutal and “on the edge of genocide”.

While the extremist group was very driven, its tactics were not sophisticated.

“The strategy here is to give … the Iraqi forces the wherewithal to do this themselves,” Air Chief Marshal Binskin said.

The opposition has backed Australia’s involvement in Iraq, which to date has included humanitarian aid drops and four deliveries of weapons to Kurdish forces.

The first ADF personnel, including commandos and the SAS, left Australia on Tuesday. The remainder will join them in the United Arab Emirates in coming days.

Labor foreign affairs spokeswoman Tanya Plibersek said the opposition’s support was not a “blank cheque” for the deployment.

She said Mr Abbott should front parliament in the next fortnight to explain Australia’s role in the international coalition, how success would be measured and when its involvement would be concluded.

“We’ve said if our involvement lasts anything more than a few weeks we should have the prime minister update the parliament,” Ms Plibersek said.

“I think it is very important that the Australian people see an end to this.”

Opposition Leader Bill Shorten, who joined Mr Abbott in Williamtown and was due to attend an event at Amberley base in Queensland, said the humanitarian mission aimed at restoring order in Iraq was important and he did not believe “mission creep” was inevitable.

Opposition Leader Bill Shorten told the ADF personnel at Williamtown they were being sent to help the displaced and protect the vulnerable.

“You go … not to assert the supremacy of one faith or one people but to defend the rights of all faiths and all peoples,” Mr Shorten said.

“Because of your skills and abilities, peace and tolerance will prevail over the poisonous hatred and fanaticism sweeping across northern Iraq.”