The commemoration on September 29 is attended by German President Joachim Gauck, European Council President Donald Tusk, and an Israeli government delegation. Ukrainian President Petro Poroshenko is hosting the events, in which representatives of some 1,000 foreign organizations are also participating. Israeli President Reuven Rivlin, who had been on a state visit to Ukraine, had to return to Israel on September 28 following the death of Israeli statesman Shimon Peres. The September 29-30 slaughter of Jewish men, women, and children at the Babi Yar ravine in 1941 was an early example of the industrial-scale murder the Nazis would employ in their quest to annihilate the Jews. Overall, up to 100,000 more people - Jews, Roma, and Soviet prisoners of war - were executed at Babyn Yar during the Nazi occupation of Kyiv, the capital of Soviet Ukraine. Ukrainian Prime Minister Volodymyr Hroysman on September 29 called on all Ukrainians to never forget the victims of Babyn Yar. "There were Jews, Roma people, Soviet prisoners of war, and fighters of the Ukrainian liberation movement among those executed by firing squads," Hroysman wrote on his Facebook page. "We remember each of them." Ukraine has been marking the 75th anniversary of the massacre with a weeklong observance during which the Verkhovna Rada, or parliament, has held three hours of hearings. Among the speakers were Ukraine's chief rabbi, Yaakoc Dov Bleich, as well as parliamentary deputies and political dignitaries. Rabbi Moshe Reuven Azman of Kyiv's Brodski Synagogue blew the traditional shofar horn on the podium in a mark of respect for the mostly Jewish victims, Radio Liberty reported.