More than 90 percent of the 4.5 million Ukrainians who fled the country are women and children, Fontaine said.
“Hundreds of schools and educational facilities have been attacked or used for military purposes,” he said. At least 142 children have been killed in the war, according to the United Nations, which acknowledges that its figures are incomplete.
Fontaine, who went to Ukraine last week, said of the invasion: “In my 31 years as a humanitarian, I have rarely seen so much damage caused in so little time.”
During his 10-day trip, Fontaine visited Lviv in western Ukraine, Vinnystria in central Ukraine and Dnipro and Zaporizhzhia in the southeast. The war “continues to be a nightmare for Ukraine’s children,” he said at a news conference Monday.
Children “have been hurt in the very places where they should be safest — their homes, emergency shelters, even hospitals,” he said.
At one hospital Fontaine visited in Zaporizhzhia, he said, the director told him that doctors have treated 22 children who had lost limbs because of the violence.
Families are risking their lives as they attempt to flee, he added, pointing to the Russian attack last week on the Kramatorsk train station, where civilians — including children — were killed as they waited to evacuate.
The majority of Ukrainian families who have managed to flee the country have gone to Poland, which has taken in more than 2.5 million refugees. Refugees are also crossing into Romania, Hungary and Moldova, among other countries. The European Union has granted Ukrainians temporary protection status that gives them the right to live and work in member states for up to three years. The refugees are also eligible to receive social welfare, housing, health care and schooling.
UNICEF has warned that children fleeing the war face a heightened risk of human trafficking and exploitation amid the chaos. Hundreds of children have crossed into neighboring countries unaccompanied, making them especially vulnerable.
In a statement Tuesday, the United Nations High Commissioner for Refugees said that it is “impossible to gauge how many Ukrainian refugee women and children might have been preyed upon by traffickers” but that so far, “known cases are thankfully few.”
The agency called on governments to scale up child protection systems to support the influence of Ukrainian children. It said it was also increasing its support for national authorities to combat trafficking and would help establish safe stopping points for refugees in countries neighboring Ukraine.
The fate of those who remain in Ukraine has been the subject of global concern and protest in Europe, as more reports emerge of Russian attacks on civilian buildings sheltering children. Russia bombed a theater in the besieged city of Mariupol last month where hundreds of civilians had taken refuge.
Secretary of State Antony Blinken referenced the theater — where “children” in Russian had been painted on the ground outside — when he accused Moscow of war crimes last month. Russian forces have also been accused of firing on cars of people trying to escape cities under attack, even when those cars have “children” scrawled on the windows.
Fontaine warned that children across Ukraine face “severely curtailed access” to services like health care, water and education. UNICEF is pre-positioning supplies across eastern Ukraine, which is bracing for a renewed Russian offensive, and sending cash to 52,000 households.
Facing a funding gap of about $59 million as of last week, the agency is appealing for more money to help address the “rapidly deteriorating humanitarian situation,” Fontaine said.