A 93-year-old former Auschwitz death camp officer will go on trial in Germany charged with at least 300,000 counts of accessory to murder, a court says.

The German defendant, Oskar Groening, will face charges over the 425,000 people believed to have been deported to the camp in occupied Poland between May and July 1944, at least 300,000 of whom died in the gas chambers.

The regional court in the northern German city of Lueneburg said the trial, expected to be one of the last of its kind, would start on April 21.

Fifty-five co-plaintiffs, mainly survivors and victims' relatives, will be represented at the trial.

Groening, then a member of the Nazi Waffen-SS, was tasked with counting the banknotes gathered from prisoners' luggage and passing them on to the SS authorities in Berlin, prosecutors said.

For this reason, he was known as the "bookkeeper" of Auschwitz.

The accused also helped remove the luggage of victims so it was not seen by new arrivals, thus covering up the traces of mass killing, according to the prosecutors.

They said the defendant was aware that the predominantly Jewish prisoners deemed unfit to work "were murdered directly after their arrival in the gas chambers of Auschwitz".

Groening told German daily newspaper Bild in 2005 that he regretted working at Auschwitz, saying he still heard the screams from the gas chamber decades later.

"I was ashamed for decades and I am still ashamed today," Groening, who was employed from the age of 21 at the camp, said.

"Not of my acts, because I never killed anyone, but I offered my aid.

"I was a cog in the killing machine that eliminated millions of innocent people."

The German office investigating Nazi war crimes sent files on 30 former Auschwitz personnel to state prosecutors in 2013 with a recommendation to bring charges against them.

The renewed drive to bring to justice the last surviving perpetrators of the Holocaust follows a 2011 landmark court ruling.

For more than 60 years German courts had only prosecuted Nazi war criminals if evidence showed they had personally committed atrocities.

But in 2011 a Munich court sentenced John Demjanjuk to five years in prison for complicity in the extermination of Jews at the Sobibor camp, where he had served as a guard, establishing that all former camp guards could be tried.

About 1.1 million people, mostly European Jews, perished at Auschwitz-Birkenau, operated by the Nazis from 1940 until it was liberated by Soviet forces on January 27, 1945.

AFP