BERLIN (Reuters) - A 96-year-old German convicted over his role in the murders of 300,000 people at the Auschwitz Nazi death camp has challenged his four-year prison sentence, arguing that imprisonment would violate his right to life, German media reported on Tuesday.

FILE PHOTO: Oskar Groening, defendant and former Nazi SS officer dubbed the "bookkeeper of Auschwitz", is pictured in the courtroom during his trial in Lueneburg, Germany, July 15, 2015. REUTERS/Axel Heimken/Pool

A German court on Nov. 29 ruled that Oskar Groening, known as the “bookkeeper of Auschwitz”, was fit to go to prison and rejected his plea for the sentence to be suspended.

Groening, who is physically frail, was sentenced to four years in prison in 2015, in one of the last cases against a surviving Nazi, but he has not been incarcerated since then because of the legal argument about his health.

Broadcaster ntv quoted Groening’s lawyer, Hans Holtermann, as saying that the latest legal challenge asked Germany’s constitutional court to determine if imprisonment would violate Groening’s right to life, given his medical condition.

He told the broadcaster that an expert had concluded that Groening was not fit enough to be imprisoned.

Holtermann could not be immediately reached for comment.

The Nov. 29 court ruling had said that enforcing Groening’s sentence would not breach his fundamental rights and added that special needs related to his age could be addressed in prison.

Groening, a former Nazi SS officer, did not kill anyone himself while working at the camp in Nazi-occupied Poland. But a court convicted him in 2015 of aiding and abetting mass murder there through various actions, including by sorting banknotes seized from arriving Jews.

He admitted during his trial that he was morally guilty and said he had been an enthusiastic Nazi when he was sent to work at Auschwitz in 1942 at the age of 21.

Some six million Jews were murdered during the Holocaust carried out under Adolf Hitler.