Australian fighter jets have dropped a record 10 bombs on an Islamic State (IS) bomb factory deep inside Iraq.

Key points: Air strike carried out on March 5 in Anbar Province, Iraq

Air strike carried out on March 5 in Anbar Province, Iraq Strike involved largest number of bombs dropped in a single mission

Strike involved largest number of bombs dropped in a single mission ADF confirms details of past efforts in Raqqa, Mosul

The attack in Anbar Province on March 5 involved the largest number of bombs dropped in a single mission since Australian forces entered the conflict.

Defence said four Australian classic hornets led an 18-strong Coalition aircraft strike, using bombs weighing 2,000 pounds each.

Vision of a similar Australian-led air attack in Raqqa on January 17 was the first the Australian Defence Force (ADF) had released of its airstrikes in Syria.

Defence's Joint Chief of Operations, David Johnston, said the January attack was against an IS cave and tunnel complex.

"It was estimated that the destruction of the complex has effectively destroyed a significant percentage of Daesh (IS) weaponry and ammunition stored for use in that area," he said.

Sorry, this video has expired Defence Force releases footage of airstrikes in Syria

The director-general of air operations, Joe Iervasi, said the ADF did not have an accurate assessment of how many people were in the cave at the time of the attack, but did not believe any of them were civilians.

"It was solely Daesh patterns of life going to and from this complex and so there was a matter of a number of weeks of dedicated surveillance to develop this as a viable target," he said.

"And to confirm there were no civilian pattern of life in the area."

Vice Admiral Johnston confirmed Australian aircraft had been involved in efforts to retake the city of Mosul, IS's main hub in Iraq.

"Part of the campaign involves the removal of some of the ground transport networks into Mosul, we have been part of the strikes associated with that," he said.

"It will be a very difficult mission."

Vice Admiral Johsnton estimated there were currently 25,000 IS fighters in Iraq and Syria, down from 30,000.