(CNN) A former Nazi SS guard known as "the bookkeeper of Auschwitz" has died before serving a four-year jail term, authorities in Germany said.

Oskar Groening , 96, was sentenced for being an accessory to murder in 2015, but never went to jail due to a series of appeals for clemency on grounds of old age and ill-health.

He died in a hospital on Friday, according to Spiegel Online. The Hannover public prosecutor's office said it had been informed of Groening's death by his lawyer.

Groening was found guilty of being an accessory to the murder of 300,000 people at the Auschwitz death camp in Nazi-occupied Poland during World War II.

He was accused of counting the cash found in the belongings of new arrivals at the camp and sending it to Nazi headquarters in Berlin.

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