WARSAW, Poland – Holocaust survivors, politicians, religious leaders and others marked International Holocaust Remembrance Day on Sunday with solemn prayers and the now oft-repeated warnings to never let such horrors happen again.

Events took place at sites including Auschwitz-Birkenau, the former death camp where Hitler's Germany killed at least 1.1 million people, mostly Jews, in southern Poland. In Warsaw, prayers were also held at a monument to the fighters of the Warsaw Ghetto Uprising of 1943.

Pope Benedict XVI, speaking from his window at St. Peter's Square at the Vatican, warned that humanity must always be on guard against a repeat of murderous racism.