A former Auschwitz guard being tried on 300,000 counts of accessory to murder has testified that it was clear to him Jews were not expected to leave the camp in Nazi-occupied Poland alive.

"I couldn't imagine that" happening, former SS Sgt. Oskar Groening told the Lueneburg state court on Thursday during the third day of his trial, the DPA news agency reported.

The 93-year-old's answer came in response to a question from attorneys representing Auschwitz survivors who have joined the trial as co-plaintiffs, as allowed under German law.

Pleas are not entered in the German system. On the first day of his trial Tuesday, Groening acknowledged sharing in "moral guilt" but said the court will have to determine if he is legally guilty.