Russia’s war on Ukraine, now in its second week, is exacting a severe toll on children, the UN Children’s Agency (UNICEF) said on Thursday.

“The use of explosive weapons in cities could quickly turn this crisis into a catastrophe for Ukraine’s children,” Afshan Khan, UNICEF’s regional director for Europe and Central Asia, said in a statement.

“There are no armed operations of this scale that do not result in children being harmed. The consequences will be tragic,” Khan said.

UNICEF said that millions of children could be caught up in the violence as the fighting intensifies in and around the country’s major urban centers.

“The conflict has also sparked massive population displacement that could soon constitute one of Europe’s largest refugee crises since the Second World War,” UNICEF said.

“Half a million children have already fled Ukraine to neighboring countries, with the number of refugees continuing to grow,” it added.

The UN agency said that children are especially vulnerable to being injured or killed when weapons and explosive munitions are used in populated areas.

Since Feb. 24, at least 17 children have been killed and 30 injured, UNICEF said.

“These are only the reports that the United Nations has been able to verify – the true number of child casualties is likely far higher,” it added.

Hundreds of homes have been damaged or destroyed, and there are reports of schools, orphanages, and health centers sustaining heavy damage, UNICEF said.

It said that humanitarian needs across Ukraine are multiplying by the hour, adding that hundreds of thousands of people are without safe drinking water because of damage to water system infrastructure, and many have been cut off from access to other essential services like healthcare.

The UN said the country is running low on critical medical supplies and has had to halt urgent efforts to curb a polio outbreak.

UNICEF said it is appealing for $276 million for its programs inside Ukraine and needs an additional $73 million to assist children in neighboring countries./aa