A new Human Rights Watch report has documented claims of torture, summary execution and other abuses of civilians by Russian forces in north-eastern Ukraine.
During visits to 17 villages in the Kyiv and Chernihiv regions, the human rights organisation interviewed 65 people, including alleged former detainees, torture survivors, families of victims and other witnesses.
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"The numerous atrocities by Russian forces occupying parts of north-eastern Ukraine early in the war are abhorrent, unlawful and cruel," said Giorgi Gogia, associate Europe and Central Asia director at Human Rights Watch (HRW).
"These abuses against civilians are evident war crimes that should be promptly and impartially investigated and appropriately prosecuted."
The Kyiv government has accused Russia of atrocities and brutality against civilians during the invasion and said it has identified more than 10,000 possible war crimes.
Russia denies targeting civilians and says, without evidence, that signs of atrocities were staged.
A Ukrainian court held a preliminary hearing on Friday in the first war crimes trial arising from Russia's invasion, after charging a captured Russian soldier with the murder of a 62-year-old civilian.
The cases documented by HRW in its latest report include allegations of 22 summary executions, nine other unlawful killings, six enforced disappearances, and seven cases of torture, while 21 civilians described unlawful confinement in inhuman and degrading conditions.
At least some of the cases documented had previously been reported on, including by the ABC.
Those interviewed by HRW included witnesses such as 66-year-old Anastasia Andriivna, from the village of Andriivka, about 40 kilometres north-west of Kyiv.
Ms Andriivna's son, Ihor Savran, was allegedly shot in the head by Russian soldiers after they discovered his old military overcoat, from when he served in the National Guard in 1993.
After the Russian forces withdrew on March 30, Ms Andriivna found his body, along with the body of his friend, Volodymyr Pozharnikov, in a barn about 100 metres from her home.
Another unlawful killing witness interviewed by HRW was Tanya Samodiy — from the Chernihiv region village of Mokhnatyn — who said Russian forces shot and killed her 17-year-old twin brothers, Yevhen and Bohdan Samodiy, and their friend, Valentin Yakimchuk, 18.
Among the examples of "unlawful confinement" in the report was Russian forces keeping about 350 civilians, almost the entire population of Yahidne village near Chernihiv city, in the basement of a schoolhouse for 28 days.
Yahidne resident Volodymyr Ivashchenko told HRW it was damp in the basement and "everyone was coughing".
"There was not enough air," Mr Ivashchenko said. "There were hundreds of people [and] nowhere to sleep. We were locked there for days at a time, used buckets as toilets. Imagine sitting on a chair for weeks, no place to even lie down."
Mr Ivashchenko's mother-in-law, Nadiia Buchenko, was one of the eight people who died in the basement. Two more died soon after being allowed out.
One of the alleged victims of torture interviewed by HRW was Oleksandr Novichenko, 35, from Hostomel, who said he was taken into custody by Russian soldiers and kept for two days in a basement, blind-folded and with his hands zip-tied together.
Mr Novichenko claimed he was repeatedly shocked with electricity while being questioned.
"The zip-tie was so tight that my wrists were swollen," he said.
"I had an open wound on my knee, and they would shock me right there … I was screaming from pain, telling them that I knew nothing, but they would go on shocking me."
International Criminal Court team headed to Ukraine
International Criminal Court prosecutor Karim Khan on Tuesday revealed a team of 42 investigators, forensic experts and support personnel had been sent to Ukraine as part of a probe into suspected war crimes.
Mr Khan said the team would "significantly enhance the impact of our forensic and investigative actions on the ground".
He said the team would improve the gathering of witness testimony, the identification of forensic materials and help ensure that "evidence is collected in a manner that strengthens its admissibility in future proceedings" at the Netherlands-based court.
Several thousand civilians are believed to have died since the invasion began on February 24. Exact figures are impossible to verify.
To be classed as crimes against humanity, attacks have to be part of what the ICC's founding treaty, the Rome Statute, calls "a widespread or systematic attack directed against any civilian population".
Mr Khan said that "now, more than ever, we need to show the law in action" in Ukraine.
The US State Department has also launched a new program to capture and analyse evidence of war crimes and other atrocities allegedly perpetrated by Russia in Ukraine.
On Tuesday, the State Department said, in a statement, that the so-called Conflict Observatory would encompass documentation, verification and dissemination of open-source evidence of Russia's actions in Ukraine.
Reports and analyses will be made available through the Conflict Observatory's website.
US President Joe Biden has hammered Russia over what he calls "major war crimes" committed in Ukraine, and has underscored his resolve to hold Moscow accountable for launching the largest land war in Europe since World War Two.
ABC/wires
