The Presidents of Poland and Germany have taken part in ceremonies on the site of the Nazi death camp at Auschwitz in southern Poland to mark the 66th anniversary of its liberation by Soviet troops.
Some 1.1 million people - jews, gays, gypsies, communists and others were murdered in the camp by Nazi Germany.
Auschwitz was the site of the largest Nazi death camp during World War II.
Deutsche Welle Radio reports President Christian Wulff was the first German president ever to speak at the Auschwitz commemoration.
"We all carry responsibility that such a breach of civilization does not happen again," he said.
Mr Wulff also met camp survivors with Polish President Bronislaw Komorowski.
"Since World War II, across the globe there has not been a single day without war," Mr Wulff said.
"This is an appeal to youth to take responsibility for what is happening. Indifference is the worst threat to democracy and liberty."
27 January marks the day when Soviet troops liberated Auschwitz-Birkenau in 1945. Around 1.5 million people were murdered there, the vast majority of them European Jews.
The anniversary was declared an international day of remembrance for the six million victims of the Holocaust by a 2005 UN General Assembly resolution.
Deutsche Welle Radio says Germany has marked the day since 1996.
Later this year, Germany will inaugurate a national memorial to Sinti and Roma (gypsies) murdered by the Nazis.
Historians estimate that between 220,000 - 500,000 Roma and Sinti were killed by the Nazis