Russia and its proxy forces in Ukraine are operating 21 detention centres to interrogate and deport civilians and prisoners of war, according to a new report.
Yale University researchers, overseen by the US State Department, used commercial satellite imagery and open-source information to identify the locations.
Ukrainian officials have consistently accused Russia of deporting hundreds of thousands of people from areas it has overrun.
"Conditions are absolutely ripe for extreme abuse," Nathaniel Raymond, who directed the research, said.
The report, seen by Reuters ahead of its publication tomorrow, identifies with "high confidence" the site, which include schools, markets and prisons. It also identifies possible graves at one prison complex.
The Humanitarian Research Lab at Yale School of Public Health produced the report, in partnership with the Conflict Observatory, which was launched in May by the US State Department to record evidence of war crimes perpetrated by Russia in Ukraine.
Mr Raymond, the lab's executive director, said the findings reveal that Russia and its proxies have established a "system of filtration" to sort people in areas that Russian has invaded, which represents a "human rights emergency".
Reports of abuses had already emerged from the sites, including at a prison complex near Olenivka, where 53 Ukrainian prisoners of war were reported to have been killed in a blast there on 29 July.
Researchers also recorded evidence of mass graves, matching the account of a former prisoner who reported that detainees were forced to dig graves at a specific site.
The Russian Embassy in Washington claimed in July that allegations about the detention of Ukrainians in occupied areas were an attempt to stoke "Russophobia" and vilify Russian armed forces.
