Almost 650,000 people in Mosul left without water after pipeline was hit during fighting between Iraqi forces and ISIL.
Fighting between Iraqi forces and ISIL fighters has cut water supplies across a large part of Mosul, affecting 40 percent of residents in the city where poorer families are already struggling to feed themselves.
Water was cut to 650,000 people when a pipeline was hit during fighting between ISIL and the Iraqi government forces trying to crush them in their northern Iraq stronghold.
"We are facing a humanitarian catastrophe," said Hussam al-Abar, member of Mosul's Nineveh provincial council, adding that 1.5 million people were still inside Mosul.
"Basic services such as water, electricity, health, food are non-existent."
Barely more than a third of the 200,000 displaced that the UN had expected in the first few weeks of the Mosul offensive have fled their homes so far.
The lack of clean drinking water could now make it difficult for residents to remain, however.
"There is no water, we drink water from the well. It's very salty and we have to boil it before we drink it," Umm Ahraf, a 45-year-old woman, told AFP news agency in the Khadraa neighbourhood on Tuesday.