Government troops are now in "full control" of eastern Mosul, according to Iraq's military, after routing Islamic State militants from that part of the city.
The commander of the Iraqi counter-terrorism forces, Lt Gen Talib Shaghati, said the success of the Iraqi forces is "unprecedented".
The advance - more than three months since the operation to free Mosul started in October - comes following a push by Iraqi troops over the past days in the last IS-held neighbourhoods in east Mosul, closing in on the Tigris River that roughly divides the city.
Mosul - Iraq's second-largest city and the Islamic State group's last urban stronghold in the country - fell to IS in the summer of 2014, when the militant group captured large areas of northern and western Iraq.
Hailing the "big victory", Lt Gen Shaghati said plans were now being drawn up to retake the western part of the city.
Stiff resistance by the militants, thousands of civilians being trapped in their houses by the fighting and bad weather had in the past slowed the advance of troops.
However, skirmishes and clashes continued in some pockets along the Tigris in eastern Mosul, according to an Iraqi special forces spokesman, who said his unit was still pushing into the Ghabat area along the river bank.
Small arms fire could be heard and at least one civilian was wounded by mortar fire.
Also, some commanders on the ground disputed Lt Gen Shaghati's claim of "full control" of eastern Mosul, with Lt Gen Abdul-Amir Raheed Yar Allah saying the eastern side "has not been fully liberated and the advance is still continuing".
Lt Gen Yar Allah, who commands army operations in Ninevah, where Mosul is the provincial capital, said the special forces "have done their duty" in eastern Mosul.
The prospect of retaking western Mosul looms heavy on Iraqi forces, despite all the support they have from the US-led coalition, and Sunni and Shiite volunteer militias.
The western half of the city is home to some of Mosul's oldest neighbourhoods, with narrow streets packed with buildings that will further complicate the urban fight.
So far in the Mosul offensive, Iraq's counter-terrorism forces, which are by far the military's most battle seasoned unit, have done most of the fighting, advancing from east of the city.
Regular Iraqi army troops are pushing from the city's south-east and northern edges, and the federal security forces from further to the west.
The operation has also left more than 148,000 people homeless, according to the United Nations. Nearly 12,500 people have been forced to flee their homes just over the past week, the UN said.
More than one million people were estimated to still be living in Mosul in October, when Iraqi forces launched the operation to retake the city.
