Ukrainian believers gather at the front of the Saint Sophia's Cathedral in Kyiv, Ukraine December 15, 2018.
Ukrainian believers gather at the front of the Saint Sophia's Cathedral in Kyiv, Ukraine December 15, 2018. Reuters / Gleb Garanich

The United Nations' cultural agency (UNESCO) said on Tuesday it had bolstered protective measures to preserve Ukraine's endangered cultural heritage in light of Russia's invasion of its neighbour.

"The first challenge is to mark cultural heritage sites and monuments and recall their special status as protected areas under international law," UNESCO Director-General Audrey Azoulay said in a statement.

To avoid deliberate or accidental damages, the agency is marking cultural sites and monuments in Ukraine with the distinctive "Blue Shield" emblem of the 1954 Hague Convention for the Protection of Cultural Property in the Event of Armed Conflict.

"The marking with the emblem of the Convention also comes from the fact that Russia and Ukraine are two countries to have ratified this important convention", Lazare Eloundou Assomo, the director of the UNESCO World Heritage Centre, told Reuters.

"International conventions, when we ratify them, we commit to respect them," he said, adding that UNESCO was monitoring all sites in Ukraine where cultural heritage could be at risk.

Partnering with the United Nations Institute for Training and Research (UNITAR), the agency assesses damage by analysing satellite imagery for priority sites which are endangered or already impacted.

A dozen such sites are already covered by the monitoring system, according to the UNESCO statement.

Of the properties included on the World Heritage List, UNESCO said it considers the Saint Sophia Cathedral in the Ukrainian capital Kyiv and related monastic buildings a priority.

UNESCO is also monitoring Odessa, a city in southern Ukraine, Eloundou Assomo said.

"We are not waiting for the media to act," he said, stressing the urgency of marking the sites.

UNESCO plans to meet on Wednesday and Thursday with Ukrainian cultural professionals, including World Heritage Site managers and museum directors, in order to determine whether they might need technical or financial assistance.