In its report, A Heavy Price For Children, Unicef called on warring parties in Iraq to protect children's rights and said the number of youngsters at serious risk in the country has increased by 1.3 million in the past 18 months.
It describes Iraq as "one of the most dangerous places in the world for children". The report said the 2014 invasion by Islamic State into large areas of Iraq's north and west and the military operation to unseat them have had a "catastrophic impact", with 4.7 million Iraqi children in need of humanitarian assistance.
"We appeal to all parties for restraint and to respect and protect children. We must help give children the support they need to recover from the horrors of war and contribute to a more peaceful and prosperous Iraq."
Unicef called for urgent action to protect children's rights in war-torn Iraq. It appealed for humanitarian access to all children across Iraq, including in IS-controlled areas, to improve education and to provide psychological and recreation programmes. Unicef said it is short of funding and is seeking £74 million for its work in Iraq throughout 2016.
Iraq is going through its worst crisis since the 2011 withdrawal of US troops. In the summer of 2014, IS militants blitzed across large swaths of the country's north and west, capturing Iraq's second-largest city of Mosul and the majority of the western Anbar province.
IS has since suffered major defeats when Iraqi forces, backed by the US-led coalition, drove the extremists out of several key cities, including the city of Fallujah, which was retaken by Iraqi forces earlier this week. IS extremists still control significant areas, including Mosul.