Before an audience containing his fellow former inmates, French President Francois Hollande, US President Barack Obama and German President Joachim Gauck, Kent added that if he could, he would insert an 11th commandment into the Old Testament: "Thou shalt not be a passive bystander."
The only politician to speak, Polish President Bronislaw Komorowski, called the extermination camp "a hell of hatred and violence".
Around 1.1 million people, a million of them Jews, but also Sinti, Roma, Soviet prisoners of war and homosexuals, were murdered at Auschwitz during the Second World War until Red Army troops liberated the camp and around 7,500 survivors in 1945.
Kent told the world leaders, assembled with blanket-wrapped survivors and their families under a tent around the railway lines leading into the death camp, that he would never forget his experiences there.
"The cries of murdered children will ring in my ears until I die," he said.
And he added that "if you, the leaders of the world, remember, then other injustices as in Darfur, Biafra or Kosovo will have no more place on this Earth."
His voice failing at times, Kent called on the world to teach children tolerance and understanding so that such crimes against humanity could never be repeated.
Gauck had earlier delivered a solemn message to the Bundestag (German parliament) at a special session on Tuesday morning, warning that Auschwitz must continue to mark "German identity", and that Germany had a special mission "to protect and value humanity. Protect and value the rights of every single person."
Obama warned against growing anti-Semitism worldwide, mentioning especially the recent mass shootings in Paris which in part targeted French Jews.
And he added that any "trivialization of the Holocaust" should serve as a painful reminder of the need to fight anti-Semitism.
Pope Francis wrote that "Auschwitz cries out with the pain of immeasurable suffering – and calls us to a future of respect, peace and encounters between peoples."
Some in Russia expressed anger that President Vladimir Putin had not been invited to the ceremony as a representative of the Soviet soldiers who drove Nazi forces out of Poland.
Instead, Putin joined a service at the Jewish museum in Moscow.
But the museum said that they had not sent any invitations and had simply asked any who wanted to be present to come forward.
Meanwhile Israeli President Benjamin Netanyahu warned any who would attack the state of Israel that "those who play with fire, will receive fire," at a memorial ceremony at the Yad Vashem Holocaust museum.
And in Germany, the first synagogue to be dedicated in the state of Brandenburg since the Second World War was the site of a special ceremony in the city of Cottbuss, where Nazis burned down the former Jewish house of worship in 1938.
The synagogue would be the "heart of the community" for the city's 460 Jewish inhabitants, state rabbi Nachum Presman told the congregation.