German prosecutors on Monday demanded three years in jail for a 93-year-old former Nazi concentration camp guard who they said was "without a doubt" complicit in the murder of more than 5,000 people during World War II.

In what could be one of the last such cases of surviving Nazi guards, Bruno Dey stands accused of complicity in the murder of 5,230 people when he worked at the Stutthof camp near what was then Danzig, now Gdansk in Poland.

Dey, who appeared in court in Hamburg in a wheelchair and wearing a black trilby, has denied any guilt for what happened at the camp.

But chief prosecutor Lars Mahnke said Dey knew about the "state-organised mass murder" happening around him and should have climbed down from the tower and handed in his weapon.

"He knew without a doubt what was going on," Mahnke said, accusing Dey of having contributed to "barely describable crimes" that evoked "horror and shame" over what human beings are capable of doing to one another.

Dey's defence has insisted he did not join the SS voluntarily before serving at the camp from August 1944 to April 1945, ending up assigned there because a heart condition excluded him from frontline service.

But prosecutors argue that his involvement was crucial to the killings, as his time in the SS coincided with the "Final Solution" order to systematically exterminate Jews through gassing, starvation or denial of medical care.

Dey is standing trial at a juvenile court because he was aged between 17 and 18 at the time.

During his testimony in May, Dey told the court that he wanted to forget his time at the camp.

"I don't want to keep going over the past," he told the Hamburg tribunal.

Judge Anna Meier-Goering had asked whether Dey had spoken to his children and grandchildren about the time he stood guard at Stutthof.

"I don't bear any guilt for what happened back then," Dey said. "I didn't contribute anything to it, other than standing guard. But I was forced to do it, it was an order."

Bruno Dey has denied any guilt for events at the Stutthof concentration camp
Bruno Dey has denied any guilt for events at the Stutthof concentration camp POOL / Daniel Bockwoldt

Prosecutor Mahnke said Dey could be proud of his children, grandchildren and great-grandchildren. "He cannot be proud that he looked away at the decisive moment," he said.

Dey acknowledged last year that he had been aware of the camp's gas chambers and admitted seeing "emaciated figures, people who had suffered", but insisted he was not guilty.

The Nazis set up the Stutthof camp in 1939, initially using it to detain Polish political prisoners.

But it ended up holding 110,000 detainees, including many Jews. Some 65,000 people perished in the camp.

Dey, who now lives in Hamburg, became a baker after the war.

Married with two daughters, he supplemented his income by working as a truck driver, before later taking on a job in building maintenance.

He came into prosecutors' sights after a landmark 2011 ruling against former Sobibor camp guard John Demjanjuk on the basis that he was part of the Nazi killing machine.

Since then, Germany has been racing to put on trial surviving SS personnel on those grounds rather than for murders or atrocities directly linked to the individual accused.

Ukrainian-American Demjanjuk was convicted of being an accessory to the murder of nearly 30,000 Jews at the Sobibor death camp. He died while his appeal was pending.

The court ruled that as a guard at the camp, he was automatically implicated in killings carried out there at the time.

The case set a legal precedent and prompted several further convictions of Nazi officers, including that of the "bookkeeper of Auschwitz" Oscar Groening.

He died aged 96 before he could be jailed.