It was the first time in over two years that Iraqi troops have set foot inside the city, Iraq's second largest.
The advance could be the start of a grueling and slow operation for the troops, who will be forced to engage in difficult, house-to-house fighting in urban areas that is expected to take weeks, if not months.
Troops entered Gogjali, a neighborhood inside Mosul's city limits, and later the borders of the more built-up Karama district, according to Maj Gen Sami al-Aridi of the Iraqi special forces. As the sun went down, a sandstorm blew in, reducing visibility to only 100 meters and bringing the day's combat to an end.
Later, al-Aridi said the troops had taken the nearby state television building, the only one in the province, and that heavy fighting broke out when they tried to continue further in to built-up areas. An official casualty report has yet to be given, but officers mentioned one dead and one wounded.
More From This Section
Mosul is the final IS urban bastion in Iraq, the city from which it drove out a larger but demoralized Iraqi army in 2014 and declared a "caliphate" that stretched into Syria. Its loss would be a major defeat for the jihadis, but with the closest Iraqi troops still some 10 kilometers from the city center, much ground remains to be covered.
Spokesman Col. John Dorrian said that the US-led coalition, which coordinates all its attacks with the Iraqis, has been observing the battlefield and has noted that IS forces can no longer move in large numbers.
"And when we see them come together where there are significant numbers we will strike them and kill them," he said during a televised press conference with Iraqi forces in Qayara, south of Mosul. Concerns over civilian casualties have led to air operations using precision munitions only, he added.