Iraqi special forces have entered Mosul University, a tactical achievement and an incremental step in battling Islamic State militants for control of the city, two Iraqi officers said.
The troops entered the university grounds early on Friday morning and managed to secure parts of the compound, which is located in eastern half of Mosul, said the officers.
Brigadier General Haider Fadhil confirmed the account and added that Iraqi forces were now taking part in fierce battles with IS fighters inside the complex.
The development comes a day after Iraqi army forces north of the city linked up with troops pushing in from the city's eastern edge.
The sprawling university compound, a symbolic landmark in Iraq's second-largest city, was once used by IS militants as a base. Iraqi officials said the militants had also used the school's chemistry laboratories to produce chemical weapons.
Iraqi special forces Lieutenant General Abdul-Wahab al-Saadi told the Associated Press that it is unclear if the complex was still being used as an IS base.
Under heavy bombardment from US-led coalition air strikes, IS has repeatedly moved bases under cover of civilians. Earlier this month Iraqi forces retook a hospital that had been converted into an IS base.
Meanwhile, south of Mosul, the United Nations warned of an oil spill, near the town of Qayara which was retaken from IS militants in August.
The fight against IS over the past two years in Iraq has left large swathes of destruction in its wake, destroying key buildings and infrastructure.
The warnings came in a report released this week on environmental damages caused by oil fires intentionally started by retreating IS militants.
UN satellite images published on Tuesday show environmental damage from the fires.
The organisation said 11 of the fires have been extinguished, but 29 continue to burn, sending thick black smoke into the air.
The report warns that the spill, described as new, is close to a tributary of the River Tigris, which in turn could mean an oil leak into the key artery, and that parts of the spill are on fire.
As the Mosul operation enters its fourth month, Iraqi forces have retaken about a third of the city that has been under tight IS control for more than two years.
While Iraqi officials initially pledged the city would be "liberated" this year, the fight is likely to last many more months.