The Stara Gradiska concentration camp ( Croatian , Serbian : Logor Stara Gradiska , cyrillic : Логор Јасеновац ) was the largest concentration camp in the Independent State of Croatia (NDH) during World War II . The camp was established by the regime Ustasha ( Ustaša ) in August 1941 and was dismantled in April 1945 . In Stara Gradiška, the highest number of victims were Serbs , Jews and Gypsies .