Civilian casualties are beginning to mount as the battle for the Islamic State-held city of Fallujah intensifies.
"A human catastrophe is unfolding in Fallujah. Families are caught in the crossfire with no safe way out," said an official of the Norwegian Refugee Council.
Iraqi forces have launched an offensive aimed at retaking the city.
At least 20,000 children are trapped inside the city, according to a statement released by the United Nations Children's Fund (UNICEF). The organization has urged all parties to ensure the safety of these children.
The U. N. refugee agency has received reports of civilians being killed in heavy shelling or buried alive under the rubble of their homes.
"There are also reports of several hundred families being used as human shields" by Islamic State militants, said UNHCR spokesman William Spindler.
Some 625 families have managed to escape the fighting since last week. Iraqi forces are separating out and screening the men, out of concern about the loyalties of those who are leaving the city after living under IS rule for more than two years.