DETMOLD, Germany -- A 94-year-old former SS sergeant admitted in court Friday that he had served as an Auschwitz death camp guard, apologizing to Nazi Holocaust survivors looking on in a German courtroom that even though he was aware Jews were being gassed and their corpses burned, he did nothing to try to stop it.

Reinhold Hanning told the Detmould state court that he had never spoken about his wartime service in Auschwitz from January 1942 to June 1944, even to his family, but wanted to use his trial as an opportunity to set the record straight.

"I want to say that it disturbs me deeply that I was part of such a criminal organization," he said as he sat in a wheelchair, talking with a weak voice into a microphone. "I am ashamed that I saw injustice and never did anything about it and I apologize for my actions. I am very, very sorry."

As he spoke, Auschwitz survivor Leon Schwarzbaum watched from about 5 metres away with a steely face, afterward saying he was happy Hanning apologized but that it wasn't enough.

"I lost 35 family members, how can you apologize for that?" the 95-year-old said. "I am not angry, I don't want him to go to prison but he should say more for the sake of the young generation today because the historical truth is important."

Hanning is charged with 170,000 counts of accessory to murder on allegations that as a guard he helped the death camp function, so can legally be found guilty of accessory to murder. Schwarzbaum is one of some 40 Holocaust survivors who has joined the trial as co-plaintiff as allowed under German law, though only one other was in court to hear Hanning.

Prosecutor Andreas Brendel said there was good evidence already that Hanning served in the camp, but that his admission Friday could help win a conviction.

"Today's statement contributed a little more to establish that he was there, because he admitted that, and more importantly to the fact that he knew about the killings in the main camp -- that also is a crucial fact," Brendel told The Associated Press.

Pleas are not entered in the German system and such statements to the court are not uncommon, and frequently help mitigate the length of a sentence. Hanning faces a possible 15 years in prison if convicted but at his age it is unlikely he will ever spend time behind bars given the length of the appeals process.

Ahead of the short statement he made himself, Hanning's attorney Johannes Salmen read a 22-page statement from Hanning detailing how his client had joined the Hitler Youth with his class in 1935 at age 13, then volunteered at 18 for the Waffen SS in 1940 at the urging of his stepmother. He fought in several battles in World War II before being hit by grenade splinters in his head and leg during close combat in Kyiv in 1941.

Hanning spoke fondly of his time at the front and said as he was recovering from his wounds he asked to be sent back but his commander decided he was no longer fit for front-line duty, so sent him to Auschwitz.

He said he didn't know what Auschwitz was at that time, but quickly found out, though he said his initial responsibility was to register patrols and work details coming and going through the front gate, far away from where the killings were taking place.

"Nobody talked to us about it in the first days there, but if someone, like me, was there for a long time then one learned what was going on," he told the court in the statement, looking down at the table in front of him as it was read aloud. "People were shot, gassed and burned. I could see how corpses were taken back and forth or moved out. I could smell the burning bodies; I knew corpses were being burned."

He was later assigned to a guard tower and said all guards had orders to shoot prisoners trying to escape, but he did not say whether he ever shot anyone himself and did not mention any specific involvement in the killings in Auschwitz, where nearly 1 million Jews and tens of thousands of others were slaughtered.

"I've tried my whole life to forget about this time," he said. "Auschwitz was a nightmare."