They include a Berlin man suspected of being a guard at the Dachau concentration camp outside Munich, and a woman suspected of being a guard at the Auschwitz death camp in Nazi-occupied Poland as well as in other camps, Zuroff said.
He would not provide further details on the suspects, citing the ongoing investigations.
The center is offering up to 25,000 euros ($34,000) for tips that lead to the arrest and conviction of war crimes suspects.
The campaign started with posters reading "late, but not too late" in Berlin, Hamburg and Cologne. Now a further 2,500 posters are being displayed in Leipzig, Munich, Magdeburg, Rostock, Stuttgart, Dresden, Nuremberg and Frankfurt.