Oskar Groening, the former SS guard known as “the book-keeper of Auschwitz”, has died at the age of 96.

Groening was convicted in 2015 of being an accessory to the murder to 300,000 Hungarian Jews deported to Auschwitz in the summer of 1944.

Despite being sentenced to four years in jail, he never served a day of his sentence because appeals for clemency on the grounds of ill health meant he avoided imprisonment.

Spiegel Online reported that Groening died on Friday in hospital and that the public prosecutor’s office in Hannover was informed of his death by his lawyer.

Groening joined the SS in 1940, working in an administrative position.

In 1942, however, he was transferred to Auschwitz, where his responsibilities included sorting and counting currencies taken from Jews arriving in the camp on their way to being gassed, as well as guarding the belongings of the arrivals while they were being sorted.

He was transferred out of the camp in late 1944.

He maintained up until the end of his life that he had never killed anyone personally.

“The trial and conviction of Oskar Gröning sent an unequivocal message that the 'bookkeeper' of Auschwitz assisted in and facilitated the murder of 300,000 Jewish men, women and children. This should never be forgotten,” said Karen Pollock, chief executive of the Holocaust Educational Trust.

“While Gröning was able to live his life until the ripe old age of 96, the same was not afforded to his victims."

For over 40 years, Groening remained silent about his wartime activities.

He later said he was at the annual meeting of his philately (stamp-collecting) club in the late 1980s when he became involved in a discussion with someone who said the Holocaust could not possibly have happened and recommended a pamphlet to him by Holocaust denier Thies Christophersen, the author of The Auschwitz Lie.

Groening mailed a copy of Christopherson’s own pamphlet back to him, having written his own commentary on it. It included the following line:

“I saw everything. The gas chambers, the cremations, the selection process. One and a half million Jews were murdered in Auschwitz. I was there.”

For the next three decades, he was a key voice in the fight against Holocaust denial, speaking frankly about what he had seen as an SS guard in the most notorious of the Nazi death camps.

Although he described himself as “morally guilty, without question” at his trial, he did not consider himself legally guilty of any crime because he had not personally killed anyone.

But the courts did find him guilty and rejected a number of appeal attempts on the grounds of age.

In one interview he gave in his later years, Groening said that the screams of those in the gas chambers had never left him.

He asked for forgiveness from God and the Jewish people.