Iraqi army units shut the last main exit out of the Islamic State groups stronghold in western Mosul, controlling access to the city from the northwest, a general and residents there said on Wednesday.
The armys 9th armoured division is within a kilometre of Mosuls "Syria Gate", the northwestern entrance of the city, a general from the unit told Reuters by telephone.
"We effectively control the road, it is within our sight," he said. Mosul residents said they had not been able to travel on the highway that begins at the "Syria Gate" since Tuesday.
The road links Mosul to Tal Afar, another Islamic State stronghold 60km to the west, and then to the Syrian border.
Iraqi forces took control of the citys southernmost bridge earlier this week, further hemming IS militants into western areas.
The army captured the eastern side of Mosul in January after 100 days of fighting and launched their attack on the districts that lie west of the Tigris river on 19 February.
If they defeat Islamic State in Mosul, that would crush the Iraq wing of the caliphate declared by the groups leader Abu Bakr al-Baghdadi in 2014.
Closing the western route further traps the estimated 750,000 civilians estimated to be living in Mosuls western areas.
According to Iraqs ministry of displacement and migration, only 16,000 of those have managed to escape since the battle for west Mosul began.
"There is serious concern for the 750,000 trapped in the densely populated western sector, with conditions worsening daily, according to reports from those who have managed to escape," Hala Jaber of the International Organisation for Migration said in a statement.
Those still in Mosul have to face ISs strict rule along with a lack of basic goods and the danger from the fighting.
"Women had to cover up, you couldnt walk in the street without a guardian. The rules were very harsh and food was very expensive - we could only afford to eat rice and bread," Baidaa said.
Fawzia Mohammed, a mother of 16 who also fled on Tuesday, said she and her family were trapped in their homes with little to eat.
"The last days were terrible. We were trapped inside by the fighting, we had no food," she said.
"The women were forced (by IS) to cover their faces, or stay at home. But that was okay - the worst was the violence, lashings, executions, cutting people," Mohammed said.