Russia has not only prevented all efforts by the international community to independently investigate the attack but also contaminated evidence at the site, according to a new report by the United Nations (U.N.) published on July 25.Prisoners of war are protected under international humanitarian law which requires their humane treatment by the detaining side, the report says. Any abuse should be transparently investigated and prosecuted — a law that the Russian government had systematically broken since the beginning of its full-scale invasion.Ukrainian authorities have called the Olenivka attack a deliberate Russian war crime, saying Russia either hit the prison with artillery or blew it up from inside.Kyiv said that days before the attack, Russians deliberately put Ukrainian members of the Azov Regiment, who were captured in Mariupol and were awaiting a prisoner exchange, to a separate part of the prison building that was later destroyed in the explosion.Russia has accused Ukraine of attacking the prison with HIMARS, a U.S.