About 300 Holocaust survivors are expected to attend an event marking 70 years since Soviet troops liberated the Auschwitz death camp.

They will be joined by world leaders later in remembering the 1.1 million people killed by Nazis at the site, along with the countless others who lost their lives during the conflict.

With all visiting survivors now in their 70s and older, this could be the last major commemoration attended in numbers. In 2005 - the 60th anniversary of the Holocaust - 1,500 victims made the trip to southern Poland.

One 88-year-old Auschwitz survivor - who will sing a memorial prayer during the commemoration - said the Holocaust was "almost impossible for a human mind to comprehend", adding that "he prays to God that we as human beings are able to learn something from it".

Another, Rose Schindler, explained how only 11 of her loved ones survived the Holocaust, out of more than 300 relatives.

Once the 85-year-old arrived at Auschwitz, she was chosen for slave labour and was given no chance to say goodbye to her parents and four siblings.

"I have no graves for my mother, sisters, my brother and my father. So this somehow is a way to say goodbye," she added.

For some survivors visiting Auschwitz on Monday, seeing the barbed wire of the former death camp was overwhelming. One survivor cried: "I don't want to come here anymore."

Vladimir Putin will be absent from the main event, amid continuing tensions between Russia and Ukraine. However, Ukrainian President Petro Poroshenko and France's Francois Hollande will attend, along with Germany's Joachim Gauck, for a day of prayer and wreath laying.

On the eve of the commemoration, Steven Spielberg spoke with Holocaust survivors in Krakow - warning of "anti-Semites, radical extremists and religious fanatics" who want to propagate hate crimes.

The director of Schindler's List, speaking weeks after four Jews were murdered at a kosher supermarket in Paris, added: "If you are a Jew today – in fact, if you are any person who believes in the freedom of religion, freedom of speech, freedom in free expression - you know that like many other groups, we are once again facing the perennial demons of intolerance."

Marta Wise - a Slovakian Jew - was sent to Auschwitz as a child. She describes the moment she realised she'd be freed: