More than 18,000 people have taken part in the annual March of the Living between the notorious Auschwitz and Birkenau death camps in Poland.
Organisers said this year's march was the biggest yet
It comes 60 years after the camps were liberated by Soviet troops.
More than one million people, most of them European Jews, were murdered by Nazi Germany in the two camps.
Israeli PM Ariel Sharon, addressing the marchers, called for people to remember that the world stood by while six million Jews died in the Holocaust.
Speaking at a memorial gathering at Birkenau after the march, he said: "Remember the victims and remember the murderers.
"Remember how millions of Jews were led to their deaths and the world remained silent."
Organisers said this year's march was the biggest yet.
The 3km (2-mile) event, marking Holocaust Remembrance Day, began in 1988.
It symbolises the death marches that took place when the Germans began emptying the camps and forcing prisoners to walk hundreds of kilometres in freezing weather with little food. Thousands died on the marches.
Mr Sharon was accompanied to southern Poland by 20 Holocaust survivors and 20 of their grandchildren, who are serving in the Israeli army.
"With me are Holocaust survivors. Men and women who survived persecution, torture, mental and physical degradation; true heroes who experience the death marches, the deportations and searches, who survived ghettos, Auschwitz, Buchenwald... concentration and death camps whose monstrous names are carved in blood in the history of our people," he said.
The prime ministers of Poland and Hungary also took part in the event. Some 450,000 Hungarian Jews were killed at Auschwitz.