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.

The U.N.'s nuclear agency says atomic material has been taken from a university in Iraq in a region controlled by Islamic militants but it does not present a health, safety or proliferation risk.