The UN refugee agency and other organisations are urgently preparing to respond "to a potential significant new flight of displaced Iraqis escaping the latest phase in the military offensive in western Mosul," UNHCR spokesman Matthew Saltmarsh told reporters.
He said that as many as a quarter million more people could be displaced as fighting escalates in the west of the city, where an estimated 750,000 civilians are living.
That would be in addition to the more than 161,000 who have fled since the October 17 start of a massive offensive against the Islamic State (IS) group, although nearly 30,000 have returned home since soldiers recently won the east of the city.
The three months it took to reconquer Mosul's east saw some tough fighting, but even deadlier battles are expected on its west bank, home to the narrow streets of the Old City and some of IS's traditional redoubts.
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The UNHCR currently has seven camps completed and two under construction, and is at the moment able to provide shelter to around 66,000 people.
Saltmarsh said the agency aimed to nearly double the accommodation available in the near term, but was waiting for land to be allocated.
By the end of March, the UNHCR hopes to be able to house 246,930 people in camps and emergency sites, he said.
The UNHCR also warned that a growing number of people were fleeing Hawija, southeast of Mosul, due to deteriorating living conditions and escalating fighting.
"Those who are leaving Hawija are facing grave dangers," he said, pointing to ambushes and improvised explosive devices, as well as reports of kidnappings along the way.