Some 300 Auschwitz survivors have returned to the site of the Nazi death camp in southern Poland to mark 70 years since its liberation.
Some 1.1 million people, the vast majority Jews, were killed there between 1940 and 1945, when advancing Soviet troops liberated it.
Ceremonies are under way at the site in the presence of foreign dignitaries.
It is expected to be the last major anniversary event survivors are able to attend in considerable numbers.
Auschwitz was liberated on 27 January 1945. It opened as a museum in 1947.
The ceremony began with a classical concert after which the survivors were applauded.
Welcoming the visitors, Polish President Bronislaw Komorowski said the Germans had made Poland a “cemetery for Jews”.
Auschwitz survivor Halina Birenbaum, born in 1929, told the assembly that her greatest duty was to “tell others how much people [in the camps] had wanted to live”.
“I lived my mother’s dream to see the oppressor defeated,” she said, condemning Holocaust denial and warning that anti-Semitism remained a threat.
Earlier, wreaths were laid at the site as ceremonies took place in other parts of Europe and at Israel’s Holocaust museum, Yad Vashem.
Paula Lebovics, an 81-year-old survivor from Encino, California, told the AP News agency that she remembered how as a small, hungry girl of 11 she was lifted up by a Russian soldier who rocked her tenderly in his arms, tears coming to his eyes.
She did not know who that soldier was but she still felt enormous gratitude to him and the other Soviet soldiers, Ms Lebovics said, adding: “They were our liberators.”
Renee Salt, 85, from north London, visited the camp for the first time 10 years ago and “buried the ghosts”, she told the BBC, and has been going back ever since.
“I’ll do it for as long as I can. Why? There are still a lot of Holocaust-deniers the world over and if we don’t speak out, the world won’t know what happened.”
In the Czech capital Prague, speakers of parliament from across the EU gathered with the European Jewish Congress to issue a declaration condemning anti-Semitism and hate crimes.
The Prague Declaration urges “zero tolerance” and advocates fighting hates crimes through education, legislation and law enforcement.