Thousands of civilians fled Mosul overnight as Iraqi forces advanced north of a sprawling military base near the city's airport on Friday.

U.S.-backed Iraqi government troops announced on Wednesday they were in "full control" of eastern Mosul.

U.S.-backed Iraqi government troops on Sunday fully liberated the sprawling complex of Mosul University, an Iraqi military spokesman said, a major step in the massive operation to retake the Islamic State group-held city of Mosul.

The militants were fighting back at the university, which they seized when they took over the city in 2014.

Stiff resistance by the militants, civilians trapped inside their houses and bad weather have slowed advances.

The United Nations says two mortar attacks in the Iraqi city of Mosul earlier this week killed four aid workers and seven other civilians.

As the battle for Mosul, ISIS' largest stronghold in Iraq, the Islamic State group is being denied access to revenue sources such as oil and gas.