Nazi-hunters were encouraged by the prosecution last month in Hungary of 98-year-old Laszlo Csatary for helping to deport Jews to Auschwitz and by the arrest in Germany of Hans Lipschis, a suspected former guard at the Auschwitz concentration camp.
"Operation Last Chance II" is the name given to the Simon Wiesenthal Center's publicity campaign, which starts July 23 and includes putting up posters in big cities to enlist the help of the public in tracking down suspects.
Rewards of up to 25,000 euros ($32,600) are on offer.
On the striking poster is a black and white photograph of the notorious "Gate of Death" at the Nazis' Birkenau extermination camp with the train tracks leading up to it. The slogan "Late, but not too late" is emblazoned across it.
"This is really it. We have two or three years maximum, that's all," Efraim Zuroff, head of the Israel office of the Simon Wiesenthal Center, told Reuters.
The hunt is no longer for high-level perpetrators of the Holocaust, in which some 6 million Jews were murdered, but for thousands of people who helped in the machine of death. Zuroff says some 60 individuals could be alive and fit to go on trial.
"I don't imagine 60 people will be brought to justice but every single one is a victory," he said. "It may be two or three or five and there is no reason to forego these.
"Every prosecution is an important reminder that justice for the victims of the Holocaust can still be done," and advanced age did not diminish guilt, he said.
The impetus for a handful of new investigations came from the landmark conviction in Munich in 2011 of Sobibor death camp guard John Demjanjuk. He was the first Nazi war criminal to be convicted in Germany without evidence of a specific crime or a victim but on the grounds that he was a guard at a death camp.
Demjanjuk, a retired U.S. mechanic born in Ukraine, had been taken prisoner by the Nazis when he was a Soviet Red Army soldier. He died in March last year aged 91.
The campaign posters, with a hotline number for anyone with information, will be on show in Berlin, Hamburg and Cologne in conjunction with outdoor advertising company WALL AG.
"Germany has a well-developed consciousness of Nazi criminality. It is one of the few countries where family members ring up with information on relatives," said Zuroff.
The Center declined to say how much the campaign cost, but said the funding came mainly from small, private donations.
On its list of Most Wanted Nazi War Criminals is Gerhard Sommer, 92, a former member of Hitler's SS suspected of being involved in the massacre of 560 civilians in Italy.
Another is Soeren Kam, who the Center says served as an officer in the SS Viking Division and took part in the murder of a Danish anti-Nazi newspaper editor. Germany has twice refused to extradite him to Denmark.
Although an international military tribunal put some of the most infamous Nazi leaders on trial soon after World War Two in the Nuremburg Trials, Germany has a patchy record on bringing its Nazi war criminals to justice.
In the last few years, however, prosecutors in some parts of Germany have actively sought out some of the last survivors.
Many Germans are keen to draw a line under the Holocaust and seal the post-war democratic identity of their nation. To many, the spectacle of Demjanjuk being rolled into court on a hospital bed was pathetic and some find it distasteful to pursue old men, often in poor health, for crimes committed nearly 70 years ago.
Others say that it is never too late and prosecution helps to fight those who still engage in denial and distortion of the Holocaust.
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