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.

`'The memory of this immense tragedy, which above all struck so harshly the Jewish people, must represent for everyone a constant warning so that the horrors of the past are not repeated, so that every form of hatred and racism is overcome, and that respect for, and dignity of, every human person is encouraged," the German-born pontiff said.

Not all words spoken by dignitaries struck the right tone, however.

On the sidelines of a ceremony in Milan, former Italian Premier Silvio Berlusconi sparked outrage when he praised Benito Mussolini for `'having done good" despite the Fascist dictator's anti-Jewish laws. Berlusconi also defended Mussolini for allying himself with Hitler, saying he likely reasoned that it would be better to be on the winning side.

The United Nations in 2005 designated Jan. 27 as a yearly memorial day for the victims of the Holocaust – 6 million Jews and millions of other victims of Nazi Germany during World War II. The day was chosen because it falls on the anniversary of the liberation in 1945 of Auschwitz, the Nazis' most notorious death camp and a symbol of the evil inflicted across the continent.

"Those who experienced the horrors of the cattle cars, ghettos, and concentration camps have witnessed humanity at its very worst and know too well the pain of losing loved ones to senseless violence," U.S. President Barack Obama said in a statement.

Obama went on to say that like those who resisted the Nazis, "we must commit ourselves to resisting hate and persecution in all its forms. The United States, along with the international community, resolves to stand in the way of any tyrant or dictator who commits crimes against humanity, and stay true to the principle of `Never Again.'"

As every year, Holocaust survivors gathered in the cold Polish winter at Auschwitz – but they shrink in number each year.

This year the key event in the ceremonies was the opening of an exhibition prepared by Russian experts that depicts Soviet suffering at the camp and the Soviet role in liberating it. The opening was presided over by Sergey Naryshkin, chairman of the Russian State Duma.

Several years ago, Polish officials stopped the opening of a previous exhibition. It was deemed offensive because the Russians depicted Poles, Lithuanians and others in Soviet-controlled territory as Soviet citizens. Poles and others protested this label since they were occupied against their will by the Soviets at the start of World War II.

The new exhibition – titled "Tragedy. Courage. Liberation" and prepared by the Museum of the Great Patriotic War in Moscow – removes the controversial terminology. It took years of discussions between Polish and Russian experts to finally complete it.

The exhibition narrates the Nazi crimes committed against Soviet POWS at Auschwitz, where they were the fourth largest group of prisoners, and at other sites. And it shows how the Red Army liberated the camp on Jan. 27, 1945, and helped the inmates afterward.

Also Sunday, a ceremony was held in Moscow at the Jewish Museum and Tolerance Center, which opened in November and is Russia's first major attempt to tell the story of its Jewish community. The museum portrays Russia as a safe and welcoming place for Jews today despite its history of pogroms and discrimination.

In Serbia, survivors and officials gathered at the site of a former concentration camp in the capital, Belgrade, to remember the Jewish, Serb and Roma victims of the Nazi occupation of the country.

Parliament speaker Nebojsa Stefanovic said it is the task of the new generations never to forget the Holocaust crimes, including those against Serbs.

"Many brutal crimes have been left without punishment, redemption and commemoration," he said. "I want to believe that by remembering the death and suffering of the victims the new generations will be obliged to fight any form of prejudice, racism and chauvinism, anti-Semitism and hatred."

___

Associated Press writers Frances D'Emilio in Rome, Jovana Gec in Belgrade and Lynn Berry in Moscow contributed to this report.

Also on HuffPost:

Loading Slideshow...
  • Flowers lay on a slab of the Holocaust Memorial to commemorate the victims of the Nazi regime at the International Holocaust Rememberance Day in Berlin, Sunday, Jan. 27, 2013. (AP Photo/Markus Schreiber)

  • White and red roses are placed on a memorial at the former Nazi concentration camp Buchenwald near Weimar, Germany, Sunday, Jan. 27, 2013. (AP Photo/dpa/Martin Schutt)

  • People gather to light candles and to attend a memorial ceremony during the International Holocaust Remembrance Day on Sunday Jan. 27, 2013, at Raoul Wallenberg Square in Stockholm, Sweden. (AP Photo/Scanpix Sweden/Leif R Jansson)

  • A woman lights a candle as she attends a memorial ceremony during the International Holocaust Rememberance Day on Sunday Jan. 27, 2013, at Raoul Wallenberg Square in Stockholm, Sweden. (AP Photo/Scanpix Sweden, Leif R Jansson)

  • A woman wearing a headscarf and playing the accordion sits in the Memorial for the Murdered Sinti and Roma under the nazis regime, in Berlin, Germany, Jan. 27, 2013. People remember the victims of the Nazi regime on the International Holocaust Day. The International Holocaust Day marks the liberation of the Auschwitz death camp on Jan. 27, 1945. (AP Photo/dpa/Soeren Stache)

  • A participant wearing a kipa, attends a memorial ceremony to remember the victims of the holocaust in Dresden, Germany Sunday Jan. 27, 2013. (AP Photo/dpa/Arno Burgi)

  • Visitors stand in front of the gate of the former nazi concentration camp Sachsenhausen in Oranienburg, eastern Germany, Sunday Jan. 27, 2013. (AP Photo/dpa/Patrick Pleul)

  • Stella Knobel

    Holocaust survivor Stella Knobel, poses next to her teddy bear during a new exhibition of Israel's national Holocaust memorial and museum in Jerusalem, Sunday, Jan. 27, 2013. (AP Photo/Ariel Schalit)

  • Holocaust survivor Stella Knobel's teddy bear on display at the memorial's "Gathering the Fragments" exhibit at Yad Vashem Holocaust memorial and museum in Jerusalem, Sunday, Jan. 27, 2013., Sunday, Jan. 27, 2013. When Stella Knobel's family had to flee World War II Poland in 1939, the only thing the 7-year-old girl could take with her was her teddy bear. For the next six years, the stuffed animal never left her side as the family wondered through the Soviet Union, to Iran and finally the Holy Land. "He was like family. He was all I had. He knew all my secrets," the 80-year-old now says with a smile. "I saved him all these years. But I worried what would happen to him when I died." So when she heard about a project launched by Israel's national Holocaust memorial and museum to collect artifacts from aging survivors - before they, and their stories, were lost forever - she reluctantly handed over her beloved bear Misiu - Polish for “Teddy Bear”- so the fading memories of the era could be preserved for others. (AP Photo/Ariel Schalit)

  • Shlomo Resnik

    Holocaust survivor 83-year-old Shlomo Resnik and his wife attend the memorial's "Gathering the Fragments" exhibit at Yad Vashem of more than 71,000 items collected nationwide over the past two years in Israel's national Holocaust memorial and museum in Jerusalem, Sunday, Jan. 27, 2013. His item was the steel bowl that he and his father used for food at the Dachau concentration camp. His father Meir's name and number are engraved on the bowl, which serves as a reminder of how hard they had to scrap for food. "We fought to stay alive," he said. (AP Photo/Ariel Schalit

  • Roses are placed in the Holocaust Memorial commemorating the persecution of the Jewish people during World War II, in Thessaloniki, northern Greece, on Sunday, Jan. 27, 2013. There were some 50,000 Jews living in Thessaloniki at the start of World War II, and almost 45,000 perished at Auschwitz concentration camp, and Greece officially commemorates the Holocaust every Jan. 27. (AP Photo/Nikolas Giakoumidis)

  • People attend a ceremony at the Holocaust Memorial commemorating the persecution of the Jewish people during World War II, in Thessaloniki, northern Greece, on Sunday, Jan. 27, 2013. (AP Photo/Nikolas Giakoumidis)

  • A rose is placed on top of a sign that reads "Stop" with a skull painted, near the gate at the concentration camp during a ceremony marking the 68th anniversary of the liberation of the Auschwitz by Soviet troops and to remember the victims of the Holocaust, in Auschwitz Birkenau in Oswiecim, Poland, Sunday, Jan. 27, 2013. (AP Photo/Czarek Sokolowski)

  • Serbian military honor guards stand to attention as people attend commemorations for victims of the Holocaust at a monument erected in the former World War II Nazi concentration camp of Sajmiste in Belgrade, Serbia, Sunday, Jan. 27, 2013. (AP Photo/Darko Vojinovic)

  • Serbian military honor guards participate in commemorations for victims of the Holocaust at the former World War II Nazi concentration camp of Sajmiste in Belgrade, Serbia, Sunday, Jan. 27, 2013. (AP Photo/Darko Vojinovic)

  • Memorial candles are lit in front of a photo taken during WWII showing refugees fleeing from the Nazis at a ceremony marking International Holocaust Remembrance Day in Russia’s first Jewish Museum in Moscow, Russia, Sunday, Jan. 27, 2013. (AP Photo/Alexander Zemlianichenko Jr)