U.N. Secretary-General Antonio Guterres, on a visit to Iraq, says that protection of civilians in Mosul must be an "absolute priority."
After his arrival in Baghdad, Guterres met with President Fuad Masum, parliament speaker Salim al-Juburi, and Foreign Minister Ibrahim al-Jaafari to discuss the "dire humanitarian situation on the ground" as a result of the operation to oust Islamic State from their stronghold.
Guterres was also due to speak with Prime Minister Haider al-Abadi before flying north to the self-ruled Kurdish region of the country.
More than a half-million civilians are still believed to remain in Islamic State-held areas of Mosul, with many of them used by Islamic State extremists as human shields as Iraqi forces advance.
Civilians, humanitarian aid groups and monitoring officials have warned about the possibility of increased civilian casualties because of a growing demand for airstrikes and artillery.
A top U.S. commander said Islamic State fighters have begun forcing civilians in Mosul into buildings rigged to explode. The U.S. is investigating reports of about 100 civilians being killed in a building collapse in Mosul that occurred the same time U.S. jets were striking IS positions in the area.