Iraq's special forces suffered significant casualties in the fight for eastern Mosul and in the first weeks of the push on Mosul's west, Iraq's federal police - relatively inexperienced in urban combat - took a lead role in one of the city's most hard districts.
Sha'aban Nasiri, a former major-general in Iran's Islamic Revolutionary Guard Corps, was killed in battle near Mosul, Joint Operation Command spokesman Col. Mohammed Ibrahim.
Thousands of Iraqi security forces, Kurdish Peshmerga fighters, Sunni Arab tribesmen and Shia militiamen, assisted by US-led coalition warplanes and military advisers, are involved in the offensive.
Civilians too have been caught in the crossfire, leaving hundreds of thousands displaced and thousands dead. More than 30 ISIL fighters were also killed in clashes.
The officers described the advance as "cautious" and the clashes on Sunday as "sporadic".
On Sunday, two Iraqi military officers reported serious obstacles, with militants deploying snipers, suicide auto bombers and suicide attackers on foot.
She said that the United Nations estimates there are between 180,000 and 200,000 civilians in jihadist-held areas of Mosul, the majority of them in the Old City area.
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Even though the Islamic State now controls only roughly 5 square miles of the city, Iraqi and USA commanders have cautioned that the worst fighting has yet to come.
However, a combination of concentrated attacks by the Iraqi military and the volunteer forces, who rushed to take arms after top Iraqi cleric Ayatollah Ali al-Sistani issued a fatwa calling for fight against the militants, blunted the edge of the Daesh offensive and in recent months led to liberation of much of the territories occupied by Daesh.
Iraqi forces have taken another step toward wrestling Mosul from ISIS.
"Civilians are going to be at the most extreme risk they have been during the entire campaign", she said.
Worldwide aid group Save the Children expressed concern that the call for civilians to leave could expose them to additional danger.
The Joint Operations Command also said Monday that Iraqi aircraft had dropped leaflets over Mosul urging residents to leave IS-held areas - the second time it had done so within the past week.
The government wants to avoid civilian casualties, who have been used by the extremist IS militant as human shields, and in order to pave the way for the security forces to free the rest of the western side of Mosul, according to the statement.
The March 17 strike sparked calls from Iraqi and world leaders for greater protection of civilians.
Checkpoints outside the city have seen a surge in civilians trying to get out.