Dozens of valuable churches, historical sites, and museums have been damaged by the war in Ukraine, the United Nations’ cultural agency said on Friday, adding that it was particularly worried about the northern city of Chernihiv.

Last month UNESCO said it had bolstered protective measures for Ukraine’s endangered cultural heritage in light of Russia’s invasion, such as using a “Blue Shield” emblem to mark its cultural sites and monuments.

"We are very concerned about both the situation at the humanitarian and (cultural) heritage levels. Humanity's heritage is in danger (in Ukraine)," Ernesto Ottone, UNESCO's assistant director-general for culture, told a news conference.

UNESCO's first, preliminary list of totally or partially damaged sites featured 29 religious sites, 16 historical buildings, four museums, and four monuments, it said.

UNESCO's chief Audrey Azoulay wrote to Russian Foreign Minister Sergei Lavrov at the beginning of March to remind him that Russia is a signatory to the convention for the protection of cultural heritage at the time of war, the agency said.

But there had been no response so far, it added.

At talks this week, Moscow, which calls its actions in Ukraine a "special military operation", said it would reduce offensives near Kyiv, the capital, and the nearby city of Chernihiv, to build trust.

Kyiv and its allies say Russia is pulling troops out of those areas, not as a goodwill gesture but to regroup because they have taken heavy losses.