It is a once-in-a-generation intake and Australian immigration officials are gearing up for a massive task.

The Immigration Department is doubling its staff numbers in the Middle East to enable the quick processing of 12,000 Syrian refugees who will be resettled in Australia.

The ABC understands that while religious persecution may be seen as a reason for protection to be granted, specific religions are not being given greater priority over others.

John Moorhouse, the regional director for the Immigration Department, told the ABC that interviews have already began to take place.

"Priority will be given to those seen to have suffered the most," he said.

Mr Moorhouse, who is in charge of coordinating Australia's largest refugee intake in years, said immigration officials will work closely with the UN refugee agency to pinpoint the neediest families.

"All of the 12,000 refugees will have to be registered with the UNHCR," he said, speaking from Dubai.

The majority of the processing will happen in Lebanon and Jordan.

Mr Moorhouse said Syrian refugees who may have relatives in Australia and have already applied under the Special Humanitarian program will be also be considered as part of the intake.

All refugees will have to pass security checks and have no criminal record.

While the vast majority of refugees are expected to come from Syria, some families from Iraq will also be eligible to be resettled.

The first arrivals are not expected in Australia for at least two months.

Australia's humanitarian intake of refugees is doubling, from 13,750 people for 2015-16, to 25,750 in the next 18 months.