Auschwitz was the largest of the extermination camps and has become a symbol of Nazi Germany's genocide of six million Jews, one million of whom died at the site between 1940 and 1945, along with more than 100,000 non-Jews.
Elderly former inmates, some wearing scarves in the blue-and-white stripes of their death camp uniforms, laid flowers at the site on Monday touching the camp's Wall of Death in silence.
Around 50 survivors are expected at the main commemoration from 1500 GMT outside the gates of Auschwitz II-Birkenau. They will be joined by dozens of leaders, including Britain's King Charles III and French President Emmanuel Macron.
According to organizers, four former inmates -- Marian Turski, Janina Iwanska, Tova Friedman, and Leon Weintraub -- will speak at the main event.
"When I arrived in Auschwitz and got off the train, I saw the pits where human corpses were burned because the crematoria could not keep up," Iwanska, a 94-year-old Warsaw-born survivor, told AFP earlier this month.
Ukrainian President Volodymyr Zelensky was also in Poland for the ceremony, and German President Frank-Walter Steinmeier, Chancellor Olaf Scholz and Israeli Education Minister Yoav Kisch are expected.
But there will not be speeches by politicians, Auschwitz Museum spokesman Pawel Sawicki told AFP.
In an anniversary statement, Zelensky said the world must unite against evil.
"It is everyone's mission to do everything possible to prevent evil from winning," he said.
Speaking to AFP ahead of the anniversary, survivors around the world spoke about the need to preserve the memory of what happened when there will no longer be living witnesses.
They also warned about rising hatred and anti-Semitism in many countries and spoke of their fears about history repeating itself.
Organizers said it could be the last major anniversary with such a large group of survivors.
"We all know that in 10 years it will not be possible to have a large group for the 90th anniversary," Sawicki said.
- 'Overcome hatred' -
Auschwitz was created in 1940 using barracks in Oswiecim, southern Poland. Its name was Germanized into Auschwitz by the Nazis.
The first 728 Polish political prisoners arrived on June 14 of that year.
On January 17, 1945, as Soviet troops advanced, the SS forced 60,000 emaciated prisoners to walk west in what became known as the "Death March".
From January 21-26, the Germans blew up the Birkenau gas chambers and crematoria and withdrew as Soviet troops approached.
On January 27, Soviet troops arrived, finding 7,000 survivors.
The day of its liberation has been designated by the United Nations as Holocaust Remembrance Day.
Until its invasion of Ukraine in 2022, a Russian delegation had always attended the annual ceremony but Moscow will be barred again this year.
There has also been controversy following rumors that Israeli Prime Minister Benjamin Netanyahu could attend the ceremony.
The International Criminal Court last year issued an arrest warrant for Netanyahu on suspicion of crimes against humanity and war crimes over the Gaza war.
The Polish government confirmed last month that it would not arrest Netanyahu if he were to visit, even though the Israeli leader has not expressed any intentions to attend.
- 'Not forgotten' -
Some 40 survivors of the Nazi camps agreed to talk to AFP before the anniversary.
In 15 countries, from Israel to Poland, Russia to Argentina, Canada to South Africa they told their stories, alone or surrounded by their children, grandchildren and great grandchildren -- proof of their victory over absolute evil.
Julia Wallach, who is nearly 100, cannot talk about what happened without crying.
"It is too difficult to talk about, too hard," she said. The Parisian was dragged off a lorry destined for the gas chamber in Birkenau at the last minute.
They were 18, 12 or 4 years old and lived through the hell of the Nazis death camps. Today, 80 years after the liberation of Auschwitz-Birkenau, survivors from around the world share their memories and their hopes, perhaps for the last time.
But hard as it is to relive the horrors, she insisted she would continue to give witness.
"As long as I can do it, I will do it." Beside her, her granddaughter Frankie asked: "Will they believe us when we talk about this when she is not there?"
That is why Esther Senot, 97, braved the Polish winter last month to go back to Birkenau with French high school students.
She kept a promise made in 1944 to her dying sister Fanny, who -- laid out on the straw coughing up blood -- asked her with her last breath to "tell what happened to us so that we are not forgotten by history".
© Agence France-Presse
