Oskar Groening
Oskar GroeningReuters

Oskar Groening, the former Nazi SS guard known as the “Bookkeeper of Auschwitz”, has filed a challenge against his jail sentence, arguing that imprisonment would violate his "right to life", AFP reported on Tuesday.

In one of the last cases against a surviving Nazi, 96-year-old Groening was found guilty in July 2015 of being an accessory to the murders of 300,000 Hungarian Jews at the death camp.

He was sentenced to four years in prison at the time but has been living at home despite the conviction as he mounted an appeal against his imprisonment.

After a court ruled last month that he was fit to serve his four-year prison sentence, his defense team has now turned to Germany's Constitutional Court, claiming that jailing Groening at such an advanced age flouted his basic rights.

"In terms of constitutional law, it should be examined if the health condition of Mr. Groening allows for his basic right to life and physical integrity to be guaranteed" if he went to jail, his lawyer Hans Holtermann was quoted as having said Tuesday.

But the case before the Constitutional Court does not trigger a suspension of the sentence, meaning that Groening could be served with the notice to go to jail at any time.

Groening worked as an accountant at Auschwitz, sorting and counting the money taken from those killed or used as slave labor, and shipping it back to his Nazi superiors in Berlin.

He also on several occasions assigned to "ramp duty", processing deportees as they arrived by rail in cattle cars.

During his trial, Groening acknowledged "moral guilt" but said it was up to the court to rule on his legal culpability.

He had previously been cleared by German authorities after lengthy criminal probes dating back to the 1970s.

In recent years, Germany has begun a crackdown on Nazi war criminals. The crackdown began following the 2011 Munich trial of John Demjanjuk, a Nazi war criminal charged of assisting in the murder of 28,060 people at the Sobibor death camp and sentenced to five years. The former Nazi died in 2012.

Among a handful of convictions in Germany since the Demjanjuk trial is that of Reinhold Hanning, found guilty of complicity in the mass murders at Auschwitz.

Hanning died at the age of 95 this year, before he could serve his jail term.