"'It is an intolerable situation," said Radhika Coomaraswamy, U.N. special representative for children

and armed conflict, who spent five days in Iraq investigating the matter, UNICEF reported in a news release.

Just 50 percent of Iraqi primary school-age students in Iraq attending school, she said, while only 40 percent of the children have access to safe drinking water.

Besides exposure to violence, many children are being recruited into armed groups, Coomaraswamy said.

Coomaraswamy urged fighting groups involved in the Iraqi conflict to release children who are under age 18. She said relief workers need to deliver aid and vital supplies freely.

"We can't wait for a stable security environment to deliver humanitarian aid because it's at crisis point," Coomaraswamy said.

She called on the Iraqi and U.S. governments, as well as the international community, to ensure safe, free access for humanitarian workers so children throughout Iraq could be helped.

"Let peace in Iraq begin with the protection of children," she said.