Iraqi forces were making gains as tens of thousands of fighters advanced on Mosul Tuesday (October 18th) in an unprecedented offensive to retake the city from the "Islamic State of Iraq and the Levant" (ISIL), AFP reported.

With the crucial battle in its second day, Iraqi commanders said progress was being made as fighters pushed on two main fronts against the jihadists' last stronghold in Iraq.

Advancing in armoured convoys across the dusty plains surrounding Mosul, forces moved into villages defended by pockets of ISIL fighters after intensive aerial bombardment by international coalition warplanes.

"Joint Iraqi forces have today liberated Qarqush, Mefraq al-Hamadaniya, al-Abbas village, Telal Rajab and al-Lazaka, south and east of Mosul, and have inflicted heavy losses on ISIL," Iraqi army chief of staff Lt. Gen. Othman al-Ghanemi said on Tuesday.

"We continue to advance towards Mosul, and we are working on executing our plan cautiously to protect civilians," he said.

The Mosul offensive was launched on Monday, with some 30,000 federal forces leading the operation.

Iraqi commanders said ISIL fighters were hitting back with suicide car bomb attacks but that the offensive was going as planned.

"Many villages have already been liberated," said Sabah al-Numan, the spokesman of the elite counter-terrorism service.

"Iraqi forces have achieved their goals and even more, but we are careful to stick to the plan and not rush this," he said.

The two main fronts are south of Mosul, where forces are moving from al-Qayyarah, and east, where another push involving peshmerga fighters is under way.