At least 243 children have died and 446 others have been injured in Ukraine since the Russian invasion began in February, the Ukrainian prosecutor general's office said on Wednesday, which marks Children's Day in Ukraine.
In addition to the deaths and casualties, at least 1,937 educational institutions in Ukraine have been damaged, with 181 of them completely destroyed, the prosecutor's statement said.
The figures are "not final" as they do not include casualties in places where "active hostilities" are ongoing and in those occupied by Russian forces.
Meanwhile, UNICEF said 3 million Ukrainian children need humanitarian assistance inside the country, as do more than 2.2 million in refugee-hosting countries.
The war has wrought "devastating consequences for children at a scale and speed not seen since World War II," said the UN children's agency in a statement.
Nearly two-thirds of children have been displaced by the conflict, added UNICEF.
"June 1st is International Day for the Protection of Children in Ukraine and across the region," said UNICEF executive director Catherine Russell in the statement.
"Instead of celebrating the occasion, we are solemnly approaching June 3 -- the 100th day of a war that has shattered the lives of millions of children," she added.
"Without an urgent ceasefire and negotiated peace, children will continue to suffer -- and fallout from the war will impact vulnerable children around the world."
The conflict has caused an acute child protection crisis, said UNICEF, with those displaced "at significant risk of family separation, violence, abuse, sexual exploitation, and trafficking."