Iraqi forces along with Shiite militias began storming ISIL's last haven in Nineveh on Tuesday.
The Iraqi air force launched air raids against the group in Tal Afar, west of Mosul, in efforts to liberate ISIL's last stronghold in the country.
The Iraqi defence ministry confirmed on Twitter that it had recently conducted air strikes against ISIL in Tal Afar.
The US department of state announced on Tuesday that Iraqi forces have taken down two drones belonging to ISIL, while also killing three fighters that were fleeing from Tal Afar.
Located approximately 60 kilometres from Mosul and the borders with Turkey and Syria, Tal Afar has been under ISIL's control since mid-2014
Some elements in the Iraqi government as well as Turkey have raised concerns about Shiite militias, who were accused of torture and killings in Sunni-majority cities,taking part in the operation.
The Iraqi prime minister, Haidar Al Abadi confirmed Hashd Al Shaabi- the Shiite popular mobilization unit, "will be actively engaged in the battle".
The militias have already began carrying out military operations to the east of Tal Afar.
While Tal Afar has been surrounded by Shiite militias since the beginning of the battle to retake Mosul, Turkey has long opposed involving them in the liberation of the town and its environs on the grounds that ISIL is likely to inflict terrible reprisals on the Turkmen population and thus ignite further sectarian divisions.
Victory in the town, where the majority of the population -- both Shia and Sunni -- is ethnically Turkmen, would mean the loss of one of its most important strongholds for ISIL.
The US department of defence announced on Sunday that Operation Inherent Resolve -- aimed at combating ISIL in Iraq and Syria - launched two air strikes on ISIL's tactical units near to Tal Afar.
The strikes managed to destroy two "vehicle-borne bomb facilities" and damaged a supply route.
Meanwhile, a powerful Iraqi Shiite militia on Tuesday said that at least 40 of its fighters were killed in an attack the previous day on its positions across the border in Syria. The militia blamed the US-led coalition for the assault but ISIL claimed its fighters had targeted the militiamen.
The deputy head of the Shiite force, known as Kattaib Sayeed Al Shuhadaa, accused US forces of carrying out the assault early on Monday
The Baghdad-based spokesman of the US-led coalition, Colonel Ryan Dillon, dismissed the allegation, tweeting, "No coalition airstrikes took place in the area at the time".
According to the deputy leader of Kattaib Sayeed Al Shuhadaa, Ahmed Al Maksousi, they were hit by artillery fire in Syria's Jamouna area, about 12 kilometres from the Iraqi border.
He said the attack was launched from somewhere close to Mosul, recently recaptured by Iraqi forces from the ISIL, and was followed by an on-the-ground assault.Forty militiamen were killed and at least 30 wounded, he said, vowing, "This act will not go unpunished."
The offensive on Tal Afar comes as the US-led coalition campaign to destroy ISIL in Iraq and Syria entered its fourth year on Tuesday , and the Pentagon believes ISIL's defeat is inevitable.
At the height of its advance, ISIL held about 104,000 square kilometres of territory and even threatened Baghdad, with many Iraqi military units collapsing in disarray as the fighters approached.
"They had eight million people who were being ruthlessly held captive by their rule and living in misery, many forced into refugee status and depravity" Pentagon spokesman Navy Captain Jeff Davis said.
In the three years since the campaign began, 70 per cent of the territory ISIL once held in Iraq has been recaptured, and 50 per cent in Syria.
"Not one inch of that territory that we have liberated has been retaken by ISIS," said Capt Davis. "ISIS is facing its inevitable defeat. We will win and they will lose".