The Iraqi military and counter-terrorism forces are now in the process of sweeping al-Qayyara air base, about 65 kilometers (40 miles) south of Mosul, the country's second-largest city.
At least 38 ISIS militants were killed in the operation to retake the base, Sabah Nouri, the spokesman for Iraq's counter-terrorism unit, said Saturday on Iraqi state television station al-Iraqiya TV.
The forces have also destroyed four trucks mounted with machine guns and detonated more than 100 improvised explosive devices, Nouri added.
Recapturing and securing al-Qayyarah -- one of the biggest air bases in Iraq -- is seen as a breakthrough in the mission to liberate Mosul, as the base can be used by the army and the U.S.-led international coalition in further missions against ISIS in the region.
It also comes just weeks after Iraq declared it had regained full control of Falluja, ISIS' main stronghold in the country, as the militant group loses more ground.
"Fled like rats from the desert"
The Prime Minister called on the people in the ancient city of Nineveh to prepare for the liberation of their villages, saying that his forces would eliminate ISIS in Mosul "the same way we eliminated ISIS in Falluja and they fled like rats in the desert," according to a statement from Abadi's office.
The operation to liberate Mosul, another ISIS stronghold in Iraq, has been months in the making and involves coordination between Iraq's military, Kurdish forces and the U.S.-led airstrikes.
The Iraqi Army launched the operation on June 18, advancing from northern Salahuddin province, recapturing a number of villages and securing safe passage for scores of families displaced from their homes, according to the statement from the prime minister's office.
U.S. President Barack Obama said last month that his administration was "not ruling out the possibility" of sending hundreds of additional troops to Iraq later this year to help train, advise and assist forces for a potential assault on Mosul, according to a senior U.S. official.