Iraqi forces have turned the tables on ISIL sympathisers captured in the city of Ramadi, taunting prisoners and forcing them to kneel in the sand and cower in fear.

The Iraqi army advanced into the Ramadi city centre overnight, backed by US-led coalition air strikes and also supported by the police and Sunni tribes opposed to the jihadists.

A video filmed by soldiers, and broadcast on Iranian TV , shows a large column of captured ISIL supporters kneel in the dirt in single file, their hands handcuffed with their heads bowed as an Iraqi army commander laughs and jeers in their faces.

More footage captured by Iraqi state TV and on fighter's smartphones shows soldiers driving down the deserted streets of the bombed-out city, cautiously entering homes to find possible booby traps and retrieving shells and rockets from abandoned ISIL positions.

Retaking Ramadi, an insurgent bastion 125km west of Baghdad, would be the Iraqi federal forces' most significant victory in the war against ISIL.

The city has been held by ISIL since May and was turned into a fortress of booby traps, sniper nets and machine gun posts.

The city is no stranger to warfare and was the location of some of the deadliest fighting against US troops a decade ago.

Iraqi counter-terrorism spokesman Sabah al-Noman told AFP he expects the city to be cleared and retaken "in the coming 72 hours".

"We did not face strong resistance, only snipers and suicide bombers and this is a tactic we expected," he said.

A victory in Ramadi would leave Mosul, Tal Afar and Fallujah as the only major Iraqi cities still in ISIL hands and further undermine the group's claim that the caliphate it proclaimed last year is expanding.