The Los Angeles-based Simon Wiesenthal Center has renewed its call for Hungary to immediately prosecute a top Hungarian war criminal who was never punished for his role in the mass murder of thousands of people during World War II, despite being convicted of war crimes more than six decades ago. The organization's chief Nazi hunter, Dr. Efraim Zuroff, has lambasted as "a travesty of justice" the Hungarian authorities' delay in prosecuting Sandor Kepiro, 94, despite his past conviction in a Hungarian court for war crimes committed in World War II. "The problem is they are acting as if they have all the time in the world, but we really don't have time," Zuroff said Tuesday. Kepiro was convicted in 1944 for his role in the murder of 1,246 civilians in the city of Novi Sad in January 1942, when he served as a gendarme with an Hungarian army unit, the Wiesenthal Center said. After details of the massacres in the region - which Hungary had annexed as a prize for its collaboration with Nazi Germany - were revealed, Kepiro was sentenced in 1944 to 10 years in jail for his role in the killings. But after the Nazi invasion of Hungary that same year, Kepiro was cleared by a Nazi-dominated military tribunal, which acquitted him and restored his ranks. He went on to become the highest-ranking gendarmerie officer in the city and participated in the deportation of Jews to Auschwitz, the Wiesenthal Center said. After the war, Kepiro escaped to Austria where he lived for three years. Kepiro then moved to Argentina where he lived for nearly half a century before returning to Budapest, where he was tracked down by the Wiesenthal Center. Last year, in a controversial ruling, a Hungarian court decided not to enforce Kepiro's six-decade-old conviction. The Hungarian government subsequently opened a new murder investigation in the case last year. "What has to happen for justice to be achieved?" Zuroff asked Monday at a memorial service in Serbia for the victims of the 1942 mass murder. "How is it possible that someone as obviously guilty as Kepiro, someone who was convicted for his role in 1944 by a Hungarian court, is still a free man, walking the streets of Budapest?" Zuroff said. Kepiro has denied the allegations against him, asserting that while he was present at the Novi Sad massacres, it was Hungarian soldiers - and not gendarmes like him - who did the shooting.