Two Israeli citizens were severely beaten by a group of skinheads in a Belgrade park in what Jewish leaders in Serbia described Tuesday as an anti-Semitic attack. The two - Jariv Avram, 27, and Bojana Petkovic, 23 - were attacked late Sunday during a rock music festival in a downtown park by several men wearing Nazi symbols, police said. Avram suffered serious head injuries, while Petkovic was bruised, the two Israelis told Belgrade media. "They were chanting 'Auschwitz, Auschwitz' and 'Go to Germany' as they attacked us," Avram said, adding that police did nothing to protect them. "This is not the first such anti-Jewish and racist attack by skinheads and other such groups" in Serbia, the Serbian Jewish Community said in a statement. It called for police to arrest the perpetrators. Serbian President Boris Tadic denounced the attack Tuesday, demanding "the identification of all ultra-right and ultra-nationalist organizations in Serbia." Serbia has seen a surge of anti-Semitism in recent years fueled by Serb nationalists. Serbia had a 30,000-strong Jewish community before World War II, but less than half survived the Nazi occupation. Many later moved to Israel or to the West.