UNICEF says more than 1,300 schools in Ukraine have been totally destroyed in Russia's invasion of the country, resulting in signs of widespread learning loss among children.

UNICEF Regional Director for Europe and Central Asia, Regina De Dominicis, revealed the figure in a news conference on Tuesday.

She said just one in three schoolchildren in Ukraine are attending classes in person full-time, while another third are learning fully online, partly due to the impact of the coronavirus pandemic.

UNICEF's survey also showed that about half of teachers in Ukraine had reported a deterioration in students' abilities in languages and mathematics.

Many Ukrainian children have fled to other countries since the start of Russia's invasion. UNICEF said more than half of such children from preschool to secondary school age are not enrolled in national education systems in host countries. It said many of them are likely to miss out on their education due to language barriers and other reasons.

De Dominicis said, "The war in Ukraine has become a war on children," who are the ones that will support reconstruction.