The state prosecutor's office in the western city of Dortmund said the two unnamed suspects, aged 92 and 93, had participated in the Nazi killing machine in then occupied Poland, according to a statement released by the regional court in nearby Muenster.
"With their actions during their time as guards at the Stutthof concentration camp, the accused are believed to have been accessories in numerous killings," the court said.
The 92-year-old suspect was stationed at Stutthof between June 1944 and May 1945, while the 93-year-old accused acted as a guard between June 1942 and September 1944.
Some 65,000 people died at the Stutthof former concentration camp, which Nazi Germany set up in 1939 outside what was is now the Polish city of Gdansk, before its liberation in 1945.
Among other crimes, the suspects are accused of involvement in the mass killing of more than 100 Polish prisoners in a gas chamber at the camp in June 1944, and of another 77 wounded Soviet prisoners of war the same summer.
They are also accused of participating in the extermination between August and December 1944 of hundreds of Jews, who had been told they were bound for a labour camp.
And they are suspected of complicity in the horrific conditions at the camp that led several hundred prisoners to contract deadly diseases such as typhus.
The Muenster court said the two accused deny involvement in the deaths at Stutthof.
It must now decide whether the cases will go to trial.
Seventy years after the trials of top Nazis began in Nuremberg, Germany is racing against time to prosecute the last Third Reich criminals to make up for decades of neglect.
However, many cases fail to end up in court because the elderly defendants are often deemed no longer fit enough to be prosecuted.
Only four suspects were taken to court in the last seven years, all using a new standard of evidence: that it was sufficient to work at a death camp to be prosecuted, even without proof of a link to specific killings.