Efraim Zuroff, the chief Nazi hunter with the Simon Wiesenthal Centre, has welcomed the arrest of Hans Lipschis over allegations he served as a Auschwitz death camp guard.
Lipschis number 4 on his current list of "most wanted Nazi war criminals".
Mr Zuroff told the Associated Press: "This is a very positive step, we welcome the arrest. I hope this will only be the first of many arrests, trials and convictions of death camp guards".
A 93-year-old man alleged Auschwitz death camp guard has been arrested by German authorities, the Associated Press reports, citing Stuttgard prosecutors.
Hans Lipschis was taken into custody after it was concluded there was "compelling evidence" he was involved in crimes at Auschwitz while there from 1941 to 1945, prosecutor Claudia Krauth said.
Lipschis has acknowledged being assigned to an SS guard unit at the camp but maintains he only served as a cook and was not involved in any war crimes.
Germany has arrested an alleged former Auschwitz guard on suspicion of accessory to murder.