“Millions are being plunged into extreme hardship and appalling conditions of life by these strikes”, he said.
“Taken as a whole, this raises serious problems under international humanitarian law, which requires a concrete and direct military advantage for each object attacked”.
According to the UN Human Rights Monitoring Mission in Ukraine (HRMMU), on Wednesday further missile strikes in the city and region of Kyiv killed at least eight civilians, counting one girl, and injured some 45 others, including seven children.
A two-day old baby boy was killed, and two doctors injured by a rocket strike on a hospital in Vilniansk, in the Zaporizhzhia region.
Since Russia began its ongoing barrage of missile strikes and loitering munition attacks across the country on 10 October, HRMMU has verified at least 77 civilian deaths and 272 injured.
In addition to documenting civilian casualties, the Monitoring Mission has been examining videos and other information surrounding alleged summary executions.
“Since Russia began its armed attack on Ukraine in February, there have been numerous allegations of summary executions by both parties of prisoners of war and others no longer participating in the fighting”, Mr. Türk said.
“Persons hors de combat, including soldiers who have surrendered, are protected under international humanitarian law and their summary execution constitutes a war crime”, he reminded.
Among some of the videos that have surfaced over the last two weeks on social media are video clips from the village of Makiivka, which show the apparent surrender of Russian forces or Russian-affiliated armed groups; a man opening fire at Ukrainian soldiers; and subsequently the dead bodies of some 12 Russian soldiers.
“Our Monitoring Mission in Ukraine has conducted a preliminary analysis indicating that these disturbing videos are highly likely to be authentic in what they show. The actual circumstances of the full sequence of events must be investigated to the fullest extent possible, and those found responsible, appropriately held to account”, said the senior UN official.
“The analysis the Mission has done to date underlines the need for independent and detailed forensic investigations to help establish exactly what happened”.
Meanwhile, the Ukrainian authorities have opened a criminal investigation into the events.
“It is essential that all allegations of summary executions are investigated fully in a manner that is – and is seen to be – independent, impartial, thorough, transparent, prompt and effective”, said Mr. Türk.
The UN Human Rights Chief also called on the parties to “issue clear instructions” to refrain from retaliation and reprisals against any prisoners of war and to ensure that these instructions are fully complied with.
“The rules governing armed conflict set out in the Geneva Conventions demand this. Order your troops to treat those who surrender and those they detain humanely”.
He flagged the devastating impacts of missile strikes by Russian forces and allegations of summary executions of prisoners of war as showing “all too plainly the intolerable human cost of this, and any other, armed conflict”.
“They are a stark reminder of why international law exists and why it must be fully complied with to prevent a descent into utter inhumanity and negation of the very idea of our human rights”, the High Commissioner stressed.