"Hundreds of thousands of children live in communities on the front lines of the war, terrified, traumatized and deprived of their basic needs," said U.N. aid chief Martin Griffiths.

"That fact alone should compel us to do everything we can to bring more humanitarian assistance to Ukraine."

The United Nations Office for the Coordination of Humanitarian Affairs (OCHA) said that more than 14.6 million people, or 40% of Ukraine's population, will need humanitarian assistance this year due to Russia's full-scale invasion.

More than 3.3 million of the people in need live in front-line communities in the east and the south of the country, including in territories occupied by Russia, access to which remains "significantly impeded", according to OCHA.

As part of the appeal, OCHA is asking for $3.1 billion to help 8.5 million people in dire need of humanitarian aid in 2024. The U.N. refugee agency is seeking $1.1 billion to support 2.3 million Ukrainian refugees and their host communities.

Russia's invasion, launched in February 2022, has forced some 6.3 million people to flee abroad. Four million people, including nearly one million children, remain displaced within the country, according to OCHA.

"Host countries continue to extend protection and include them in society, but many vulnerable refugees still need help," said Filippo Grandi, the U.N. High Commissioner for Refugees.

"They shouldn't feel pressed to return because they cannot make ends meet in exile."

(Reporting by Gabrielle Tétrault-Farber; Editing by)