A former Nazi SS guard dubbed the "Bookkeeper of Auschwitz" is appealing against his sentence for being an accessory to the murders of 300,000 people, claiming jail would violate his "right to life".

Oskar Gröning, 96, was ruled fit to serve his four-year sentence in August after being found guilty of crimes relating to the mass killing of Jews in the Nazi concentration camp during the Second World War.

Despite being found guilty in July 2015, Gröning has been living at home due to his age and medical complications while he mounts an appeal against imprisonment.

His defence team have now launched a challenge at Germany's Constitutional Court, claiming a jail term would violate the 96-year-old's basic rights.

His lawyer Hans Holtermann told the DPA news agency: "In terms of constitutional law, it should be examined if the health condition of Mr Gröning allows for his basic right to life and physical integrity to be guaranteed [if he went to jail]."

A court doctor previously ruled he should be able to serve his sentence if he is given appropriate nursing care while in detention.

Gröning's sentence will not be suspended while the challenge is being disputed, meaning he could still be forced to go to jail at any time, reports The Local.

Gröning admitted serving in the Auschwitz concentration camp in the role of an accountant in the headquarters staff but denied his duties constituted "assistance" in the genocide.

He admitted "moral guilt" in knowing what was occurring inside the concentration camp, but ruled it was up to the court to decide on whether he was legally culpable.

He was brought to trial following the landmark case of John 'Ivan' Demjanjuk, who was convicted in 2011 of assisting the murder of almost 30,000 Jews during his service as a guard at the Sobibor extermination camp.

He was convicted not only for the atrocities he was known to have committed, but also for all the other guards who worked at the camp. Demjanjuk died in 2012, but the verdict opened up a new wave of convictions of several elderly Nazis respsonsible for the mass murder of Jews.

One million European Jews died between 1940 and 1945 at Auschwitz in southern Poland, as well as a further 100,000 Polish political prisoners, Soviet prisoners of war, Gypsy families, homosexuals and people with disabilities.

Oskar Gröning
Oskar Gröning on first day of his trial forbeing accomplice to the murder of 300,000 people at Auschwitz Andreas Tamme/Pool