Russia's claimed annexation of Ukrainian territory will only exacerbate human rights violations, the UN rights office said Tuesday as it outlined the "unspeakable suffering and devastation" inflicted on Ukrainians.

Christian Salazar Volkmann, presenting a report on Ukraine to the UN Human Rights Council in Geneva, said UN experts had documented "a range of violations of the rights to life, liberty and security".

"The Russian Federation's wide-scale armed attack has resulted in a dire human rights situation across Ukraine," the UN rights office's field operations chief said.

"The people in Ukraine have experienced unspeakable suffering and devastation."

He said the office's Human Rights Monitoring Mission, which has been present in Ukraine since 2014, had documented 6,114 civilians killed since Russia's full-scale invasion of Ukraine on February 24, stressing though that "the real figures are likely considerably higher."

"The Russian Federation's armed attack has caused the death of thousands and brought about widespread destruction of civilian objects and infrastructure," Salazar Volkmann said.

And he warned that the situation would only get worse as Russia pushes forward with finalising the annexation of the Ukrainian regions of Donetsk, Lugansk, Kherson and Zaporizhzhia, following hastily-arranged referendums dismissed as a "sham" by the West.

"With the purported annexation... the Russian Federation has taken steps which deepen rather than resolve the conflict, and exacerbate the human rights violations associated with it," Salazar Volkmann said.

- Scale of damage, destruction -

The UN rights office's 34th report on the human rights situation in Ukraine covering February 1 to July 31 this year, shows that civilians were bearing the brunt of the hostilities, Salazar Volkmann told the council.

He said the vast majority of documented civilian casualties were caused by explosive weapons being used in populated areas, "for the most part by Russian forces and affiliated armed groups".

"The sheer scale of damage and destruction is a strong indication that violations have occurred," he said.

He said people were being "forced to live in degrading conditions", unable to access their rights to housing, education, health, food and water.

The official said "disturbing accounts" were now emerging of violations in detention, of both civilians and prisoners of war, while enforced disappearances and arbitrary detention had become "widespread" in territory controlled by Russia and its proxies.

"Appalling reports of torture and ill-treatment" of civilians and POWs continue, with two documented cases of Ukrainian servicemen having been "tortured to death", he said.