Bachelet's office continues to investigate allegations of violations of international human rights law and international humanitarian law in Ukraine, "many of which may amount to war crimes," she said during a Human Rights Council special session on Ukraine in Vienna.

Photo Mariupol: wounded soldiers trapped inside Azovstal plead for help

In areas of intense hostilities, like Mariupol, it has been difficult for her team to get access and collect information, said Bachelet.

In the Kyiv region, the killing of civilians "often appears to be intentional, carried out by snipers and soldiers," she said.

Last week, her team visited 14 towns and villages in the Kyiv and Chernihiv areas, and "heard first-hand accounts of relatives, neighbors and friends being killed, injured, detained and disappeared," she said.

"To date over 1,000 civilian bodies have been recovered in the Kyiv region alone. Some of those people have been killed in hostilities, others appear to be summarily executed," and others appear to have died due to stress from hostilities and the lack of medical aid, she said. Some appeared to have been tortured, she added.