Warsaw (AFP) - US pop princess Katy Perry said Thursday she was full of emotion as she visited Auschwitz, the infamous World War II-era Nazi German death camp in southern Poland that has come to symbolise the Holocaust.

"My heart was heavy today. For ever (sic) let this place be a cry of despair and a warning to humanity," Perry said in a post on her official Twitter account linked to a photo of the camp taken during her visit Wednesday and showing its barbed-wire fences and red brick buildings.

Fresh from her highly publicised US Super Bowl half-time show, the 30-year-old singer is currently on her marathon 12-month Prismatic World Tour ending in May.

Elderly Holocaust survivors returned last month to the death camp 70 years after its liberation, to urge the world never to forget one of history's worst atrocities.

Part of Adolf Hitler's genocide plan against European Jews, dubbed the "Final Solution", Auschwitz-Birkenau was operated by Nazi Germany in the occupied southern Polish town of Oswiecim between June 1940 and January 1945.

Of the more than 1.3 million people held there, some 1.1 million mostly Jewish prisoners perished, either in the gas chambers or by starvation or disease.

Historians estimate that up to 150,000 ethnic Poles were also held at Auschwitz. Used as slave labourers, half died at the camp. Soviet prisoners of war were also imprisoned there as were homosexuals.