Mosul is the last major urban center in Iraq still under Daesh control after Iraqi forces raised the national flag over government headquarters in the heart of Fallujah Friday.
Iraqi commanders announced the launch of an offensive to retake Mosul and surrounding Nineveh province in March but under domestic political pressure the government diverted its forces to Fallujah, just west of Baghdad, last month.
"We started at 5 a.m. the second phase of the liberation of Nineveh," Iraq’s Defense Minister Khaled al-Obeidi told AFP.
"The target of the operation is to take Qayyarah and make it a launchpad for Mosul," Obeidi said.
Qayyarah, which has an airfield, lies across the River Tigris from the main base for pro-government forces in the Kurdish-controlled area of Makhmur.
It is some 60 kilometers (35 miles) south of Mosul.
On Friday, Iraqi Prime Minister Haider al-Abadi promised that the liberation of Mosul was "very near" as he declared victory in the four-week offensive to retake Fallujah.
Abadi said that only small pockets of Daesh resistance remained to be cleared from the extremists' emblematic bastion.
But Daesh still firmly controls northern neighborhoods of Fallujah where it is believed to be holding thousands of civilians as human shields.