Prime Minister Tony Abbott has confirmed Australia will extend its campaign of air strikes from Iraq into Syria, at the same time as announcing plans to "move quickly" to accept an extra 12,000 refugees affected by the conflict in both countries.

The extra permanent resettlement places will almost double this year's refugee intake, and the boost is expected to cost the federal budget $700 million over the next four years.

Key points: Australia to accept 12,000 refugees

Australia to accept 12,000 refugees Will give $44 million in financial aid

Will give $44 million in financial aid RAAF gets go-ahead for air strikes in Syria

A senior government official has told the ABC it is hoped the first refugees will arrive before Christmas, but the department also has a significant existing caseload.

The Government will also provide $44 million in financial aid for refugee agencies — in the form of food, supplies and cash — as people living in refugee camps prepare for the winter.

The extra measures have been warmly received by the Opposition and refugee groups.

"The Prime Minister's announcement comes at a crucial time when UNHCR is stretched to capacity in meeting the needs of the most desperate," the United Nations refugee agency said in a statement.

Mr Abbott's announcement on accepting an extra 12,000 refugees comes just days after he ruled out such a move.

He also stressed the need to move beyond a purely humanitarian response, and ramp up military action in Syria.

"We have to act with our heads as well as with our hearts," he said.

"As a free and democratic country, we must stand against those who wish to destroy life and to build a terrorist state."

The Government maintains the legal basis for the extended air strikes is the "collective self-defence" of Iraq, and predicts Australia could begin contributing to the campaign in Syria within a week.

"I emphasise that our aircraft will be targeting Daesh, not the Assad regime, evil though it is," Mr Abbott said.

"This is very much in Australia's national interest.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 7 minutes 17 seconds 7 m Veteran correspondent Robert Fisk shares insights into Islamic State terrorists

"Destroying this death cult is essential, not just to ending the humanitarian crisis in the Middle East but also to ending the threat to Australia and the wider world."

Conservative Queensland backbencher George Christensen said he has been reassured sleeper agents for the IS group would not be smuggled into Australia as part of the intake.

"I am very worried that if there wasn't those background checks there could be people who come here with values and motives we very much would not like to have in our country," he said.

Syria has been embroiled in a vicious civil war since a popular uprising against dictator Bashar al-Assad in 2011.

More than 200,000 people have been killed and an estimated four million have been forced from their homes amid fighting between Mr Assad's forces, Islamic State and other Islamist militants, and other rebel groups.

Opposition Leader Bill Shorten received a personal briefing from the Prime Minister about the decision.

"The swamp of terrorism can never be drained by military methods alone," Mr Shorten told Parliament.

"Labor will support this proportional action within international law," he said.

"This decision is not taken lightly."

He said Labor's support is conditional, and Australia's methods must be "strategically, legally and morally sound".

"The ADF operations have to be constrained to the collective self-defence of Iraq," Mr Shorten said.

"Further, the use of force must be limited to what is necessary to halt these cross-border attacks and defend Australian personnel."

Mr Shorten said he as also been assured of effective search and rescue provisions for Australian personnel.

Australian officials to start identifying candidates for new refugee places 'shortly'

The Government is preparing to send officials to the Middle East region to work with the UNHCR to start identifying candidates for resettlement, but Mr Abbott would not identify a timeframe for places to be filled.

Under current policy the Federal Government committed to increase the existing refugee intake of 13,750 people to 18,750 by 2018.

The Government has confirmed the 12,000 places will come on top of that previous commitment.

It is not clear whether the full intake will be immediate or whether it will be staggered over a number of years.

"We will move very quickly, but everyone who is resettled in Australia will be subject to the usual security, health and character checks," Mr Abbott said.

"We're not putting a timetable on it because we do have to make all of these important checks.

"Our focus for these new 12,000 permanent resettlement places will be those people most in need of permanent protection — women, children and families from persecuted minorities who have sought refuge in Jordan, Lebanon and Turkey... the most vulnerable of all."

"It is important that we bring in people who are going to be contributors to the Australian community, it is important that we don't bring in anyone from this troubled region who might ultimately be a problem for the Australian community."

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Labor had called for an extra 10,000 refugees to be accepted and The Greens argued for double that figure.

Yesterday Mr Abbott promised a "generous" boost in the number of refugees and emphasised the Government's policy would be informed by meetings Immigration Minister Peter Dutton held in Europe.

Foreign Minister Julie Bishop and Assistant Treasurer Josh Frydenberg had suggested considering issuing temporary visas, along the lines of the assistance provided to the Kosovars under the Howard government in 1999.

Pyne says Government 'colour blind' on refugee religion

Government ministers previously flagged that the focus of the refugee intake would be minorities that are largely Christian.

One backbencher said the message to the Prime Minister was "no more Muslim men".

But Cabinet minister Christopher Pyne stressed the Government was not focused on singling out one religious group.

"Religion is not the issue here, the issue is persecuted ethnic and religious minorities," he said.

"We have a colour-blind policy in terms of humanitarian support."

Mr Abbott has echoed that position.

"Some Muslim people are very much members of persecuted minorities, as I said, there's Druze, there's Kurds, there's Turkmen, there's Yazidi," he said.

"There are Muslim and non-Muslim persecuted minorities in this part of the world and we are prioritising all of them."

Government backbencher Cory Bernardi said Christians were in most need.

"The most vulnerable people in the Middle East are persecuted Christians, women, children and families," Senator Bernardi said.