The United Nations human rights chief voiced horror Monday at images of dead bodies in the Ukrainian town of Bucha following a Russian retreat and warned of possible war crimes.
"I am horrified by the images of civilians lying dead on the streets and in improvised graves in the town of Bucha in Ukraine," Michelle Bachelet said in a statement.
"Reports emerging from this and other areas raise serious and disturbing questions about possible war crimes, grave breaches of international humanitarian law and serious violations of international human rights law," she said.
Ukrainian authorities in Bucha said they had been forced to dig communal graves to bury the dead accumulating in the streets, including some found with their hands bound, in scenes that sent shockwaves around the world more than a month into Russia's invasion.
The scale of the killings is still being pieced together, but Ukrainian prosecutor general Iryna Venediktova said the bodies of 410 civilians had been recovered so far.
The UN rights office said Sunday that its staff on the ground had not yet been able to verify the numbers or details reported by Ukrainian officials.
"It essential that all bodies are exhumed and identified so that victims' families can be informed, and the exact causes of death established," Bachelet said.
"All measures should be taken to preserve evidence," she added.
"It is vital that all efforts are made to ensure there are independent and effective investigations into what happened in Bucha to ensure truth, justice and accountability, as well as reparations and remedy for victims and their families."
The Kremlin on Monday rejected accusations that Russian forces were responsible for killing civilians near Kyiv and suggested images of corpses were "fakes."
"We categorically reject all allegations," Kremlin spokesman Dmitry Peskov told journalists.
Peskov said that Russian "experts at the Ministry of Defence have identified signs of video fakes and various fakes."
"We would demand that many international leaders do not rush to sweeping accusations and at least listen to our arguments," he said.
International journalists over the weekend found corpses in civilian clothes, some with their hands bound, in the town of Bucha outside Ukraine's capital after Kyiv's forces retook it from Russia's Army.
Russia's Foreign Ministry has called for a special UN Security Council meeting Monday to address what it said was a "heinous provocation" to blame Russian forces.
Russian investigators also announced a probe into the images, saying that according to Moscow's military they "do not correspond to reality and are provocative in nature."