The UN Special Adviser on the Prevention of Genocide on Wednesday expressed her dismay and condemnation of possible "war crimes" by Russian troops in Bucha, a town near Ukraine's capital Kyiv.

Alice Wairimu Nderitu echoed messages by the UN secretary-general, high commissioner for human rights, and resident coordinator in Ukraine after footage of dead and mutilated civilians and mass graves emerged this week near Kyiv.

They called for an immediate cease-fire and an effective and independent investigation leading to criminal accountability over the killing of civilians in this location.

"At the same time, the Special Adviser alerted on the impact of this crisis in other regions in Europe," said a UN statement.

"Specifically, she called on all actors in position of responsibility to strengthen efforts for prevention in the region of the Western Balkans, in light of existing concerns and grievances from the painful legacy of the past being exacerbated by dynamics of deterioration associated to the ongoing conflict in Ukraine."

The Russia-Ukraine war, which started on Feb. 24, has drawn international outrage, with the EU, US, and Britain, among others, implementing tough financial sanctions on Moscow.

The UN fatality count in the Russia-Ukraine war hit 1,563 on Wednesday, including 63 children and 2,213 injured, but the real toll is much higher, says the UN./aa