Islamic State deploying 'Mad Max' vehicles

Islamic State suicide bombers are increasingly deploying "Mad Max" style vehicles against Iraqi forces in the battle for the city of Mosul, a Senate committee has been told.

Car bombs with lots of steel around them and slits for drivers to see through were often the first line of defence for IS, Australia's defence force chief Mark Binskin said on Wednesday.

Commercially-available drones armed with grenades were also a growing threat for Iraqi forces and their US-led coalition trainers including those from Australia, he said.

While east Mosul has been liberated, an estimated 750,000 civilians are under siege across the Tigris River in the city's west.

Australian and New Zealand soldiers have so far trained seven Iraqi brigades fighting to take back Mosul.

A total of 19,000 Iraqi soldiers have gone through training at the Taji base along with 1900 police.

Air Chief Marshal Binskin said Australian trainers were noticing increased confidence in Iraqi soldiers as they gained more battle experience.