"We've been trying to set up more and more camps in the area around Mosul. Those are themselves rapidly filling up to capacity. So we do need the facilities so that we can provide people with safe camps that have the resources that they need," Haq told the RT broadcaster.
Haq also said that the UN needed as many resources on the ground as possible as it would allow it to accommodate more people.
Haq said the residents of Mosul should have an opportunity to leave the city freely.
According to Haq, about 180,000 people have already left the city, which used to be one of the most populous in Iraq.
Iraqi government forces are moving forward in western Mosul, which remains partly controlled by the Islamic State terrorist group, outlawed in many countries, including Russia. The eastern part was freed in January.