Israel has marked the start of Holocaust Remembrance Day, with a ceremony for the six million Jews killed by the Nazis in World War Two. Prime Minister Benjamin Netanyahu vowed that Holocaust deniers would not be allowed to carry out a second genocide against the Jewish people.And President Shimon Peres denounced Iranian President Mahmoud Admadinejad’s appearance at the UN anti-racism conference in Geneva as a “disgrace.” “The gas has dissipated but the poison remains,” he told the service, at the Yad Vashem national memorial. Holocaust survivors were among those attending the annual state ceremony in Jerusalem, which ushers in a day of remembrance. This year, young victims are the central theme of the commemorations. One and a half million Jewish children died in the Holocaust.