Over 20,000 people from Austria and 51 other countries gathered Sunday at the Mauthausen concentration camp in north Austria to mark the 60th anniversary of the Nazi defeat in World War II.

The ceremony began when the gate of the Mauthausen camp reopened at midday Sunday, in a symbolic reenactment of the liberation by Allied troops on May 5, 1945.

Survivors, veterans, representatives of various countries and members of youth groups filed into the central square of the camp and laid wreathes in honor of the 100,000 victims of the largest Nazi concentration camp in Austria and its 49 subsidiaries.

Among them were over 100 Polish survivors who rushed to Mauthausen despite their fragile health. They attended the commemoration to pay tribute to the victims, keep alive the memories about the war and prevent a repeat of history.

About 80,000 Polish people were said to be held in Austrian concentration camps during the Second World War, 30,000 of which died there.

Austrian President Heinz Fischer delivered a speech at the ceremony and thanked the Allies for their help. He said such evil must never again be allowed to happen, recalling half of the prisoners in Mauthausen did not survive.

"Remembrance must serve as a bulwark against evil," Fischer said.

Spanish Prime Minister Jose Luis Rodriguez Zapatero, the only foreign leader present at the gathering, said: "Our task is to ensure that the children of our children will not forget this barbarism."

"Never again the horror of totalitarianism, of war and of fascism," added Zapatero.