The former prisoners entered the camp site, located in southern Poland, through the main gate bearing the notorious inscription "Arbeit Macht Frei" (“Work sets you free”).
Many of them had scarves with white and blue stripes, an echo of the striped uniforms that camp prisoners wore.
Among those who laid flowers was Jadwiga Bogucka, who was taken to Auschwitz from Warsaw in August 1944, when she was in her teens.
"I came to pay tribute to those who did not make it out of here,” she said on Wednesday. “As long as I have the strength I will continue to come here. Thank God that I survived. "
Over 1.1 million people, mostly European Jews, as well as non-Jewish Poles, Roma and Sinti, Soviet POWs and people of many other nationalities, perished at Auschwitz at the hands of Poland’s Nazi German occupiers during World War II.
The camp was liberated on January 27, 1945, by the Soviet army.
The central theme of Wednesday’s commemorations was “A return to life.”
"After the liberation, it was hard. On the one hand there was joy that I could return home, but there was no home,” Bogucka said.
“After the Warsaw Uprising everything had been burned down,” she added, referring to the 1944 operation by the Polish resistance attempting to oust the Polish capital’s German occupiers.
In 2005, the United Nations designated 27 January as International Holocaust Remembrance Day.
Although the Auschwitz camp was located in southern Poland, it was run by German Nazis, who occupied Poland in World War II. The use of the term "Polish concentration camp'"by international media outlets has inspired numerous complaints from Poland in recent years, prompting some news agencies to change their style guidelines.
In 2007, following a Polish request, the World Heritage Committee attempted to clarify the matter by listing the Auschwitz camp as a "German Nazi Concentration and Extermination Camp."