Human Rights Watch says it has documented a litany of alleged crimes against civilians in the Kyiv and Chernihiv regions of northern Ukraine.

A HRW team visiting the area in April and May said it “investigated 22 apparent summary executions, nine other unlawful killings, six possible enforced disappearances, and seven cases of torture,” according to a report released Wednesday, CNN reports.

The alleged crimes are believed to have been carried out in February and March by Russian troops as they controlled much of the area.

HRW said it had interviewed 65 people between April 10 and May 10, including the families of victims and people who said they had been detained and tortured by Russian troops.

The group said it has compiled physical evidence further implicating Russian troops in “numerous violations of the laws of war that may amount to war crimes and crimes against humanity.”

Among testimonies collected by HRW was that of 66-year-old Anastasia Andriivna from the Kyiv region, who said she found her adult son’s body in a barn after he was apparently executed.

“He was lying there in a fetal position, with his hands tucked under his head, and his jacket draped over his shoulders,” Andriivna told HRW.

The organization also reported testimony from villagers who said they were among 350 people kept for 28 days in a cramped and squalid basement in Yahidne, near Chernihiv. Other villagers there were killed by Russian troops, HRW said.

HRW's Europe and Central Asia director Giorgi Gogia called the alleged Russian atrocities “abhorrent, unlawful and cruel.”

These abuses against civilians are evident war crimes that should be promptly and impartially investigated and appropriately prosecuted,” Gogia said.