The arrest in Germany this week of a 93-year-old alleged former Auschwitz guard on charges of complicity in mass murder reopened an emotional debate on whether a measure of justice can be too late in coming.

Holocaust survivors and historians hailed the twilight bid to bring the last war criminals to book, but some have raised quiet doubts about the purpose of hauling the elderly and frail before a court.

State police took the white-haired, bespectacled Hans Lipschis, number four on the Simon Wiesenthal Center's list of most-wanted Nazis, into custody Monday after a medical examination showed he was fit to withstand detention.

A widower, Lipschis has lived for three decades in the southwestern riverside town of Aalen.

Prosecutors now say that he is "strongly suspected" of having served as a guard in the Nazi death camp from autumn 1941 until its closure in 1945.

Lipschis told a German newspaper last month that he had been at Auschwitz but "worked as a cook, the whole time".

Nearly 70 years on, the authorities opted not to release him on his own recognisance, expressing concerns he could skip bail.

Using a principle set by the landmark 2011 verdict against former Sobibor guard John Demjanjuk, which stated that simply having worked at an extermination camp is enough to establish complicity in murder, the German justice system is now investigating around 50 suspected ex-Auschwitz guards.

Most aged around 90, they could in theory still face convictions and jail time.

Since the end of the war and the US-run Nuremberg trials, German investigators have examined tens of thousands of files, but most cases were eventually dropped.

The International Auschwitz Committee, which represents survivors, said the new probes were "late, but it is not too late".

The Simon Wiesenthal Center called Lipschis's arrest "a welcome first step in what we hope will be a large number of successful legal measures".

Wolfgang Benz, former head of Berlin's Centre for Anti-Semitism Research and one of Germany's most prominent Holocaust scholars, said it was clear that every case of complicity in genocide had to be chased down.

"If Germany is a state under the rule of law then every case of murder must come before a court regardless of how old the man is, regardless of what he's been doing for the last 50 years," he told AFP.

The federal office probing Nazi crimes in the southern city of Ludwigsburg, founded in 1958, wrapped up two preliminary investigations against alleged Auschwitz guards last year and handed them to the relevant regional prosecutors.

The chief of the Ludwigsburg office Kurt Schrimm told AFP last month that his team was also actively hunting down guards from other camps.

A previous probe against Lipschis failed to establish personal involvement in murder, but the Demjanjuk case lowered the bar for prosecution.

The Ludwigsburg office says 106,000 members of the Nazi party or Wehrmacht armed forces have been accused of war crimes since 1945, of whom around 13,000 have been indicted. Only about 6,500 have been convicted.

"The fact is of course that criminal prosecution of former Nazis was long not taken seriously enough," historian Albrecht Kirschner, who is leading a commission investigating the German justice ministry's own Nazi-era history, told AFP.

He said a desire by the post-war generation to quickly move on and the sizeable presence of former Nazis in the judicial system had let thousands get off scot-free.

However renowned French Nazi hunter Serge Klarsfeld said he had mixed feelings about this late German scramble.

"I am torn between my idea of justice and the necessity to chase down war criminals until they take their last breath," he told AFP.

The daily Stuttgarter Zeitung, a respected regional broadsheet, said the 11th-hour attempt to make a man in his 90s answer for his distant past made many "uneasy".

"Justice is served in only a very limited way when old men, shortly before their deaths, are hauled before a court," it wrote.

"The sentences will only be symbolic. Above all, each of these trials will point the finger at the German federal justice system which for far too long failed to contend with the worst crimes."

However Benz said ultimately Germany's hard-won post-war integrity was on the line.

"If we only built memorials and held pretty speeches but let murderers from Auschwitz go free, then we would lose all credibility in our policy of coming to terms with our past," he said.