A "final effort" is under way in South America to track down and prosecute ex-Nazi war criminals before they die.
An estimated six million Jews were murdered in the Nazi death camps
Operation Last Chance - a scheme devised by the Simon Wiesenthal Center - attempts to locate Nazis in hiding.
It takes the form of a media campaign and offers financial rewards for any information that results in conviction.
The four countries involved are Chile, Uruguay, Argentina and Brazil - where large numbers of Nazis are thought to have fled following World War II.
The operation - launched in Lithuania, Latvia, and Estonia in July 2002 - has so far provided the names of 488 suspects from 20 different countries, the Simon Wiesenthal Center said.
According to the group, 99 cases have been submitted to local prosecutors, resulting in three arrest warrants, two extradition requests and dozens of ongoing investigations.
Simon Wiesenthal survived the Nazi death camps of World War II
"Given the large number of Nazi war criminals and collaborators who escaped to South America, the launching of Operation Last Chance has the potential to yield important results," said the Center's chief Nazi-hunter Efraim Zuroff.
The operation will formally launch at a press conference in Buenos Aires, Argentina on Tuesday.
The center's founder, Holocaust survivor and Nazi-hunter Simon Wiesenthal, died two years ago.
He was credited with helping to bring more than 1,100 Nazi war criminals to justice in the decades after the genocide of the Jews in World War II.
Six million Jews were murdered in the Nazi death camps, along with hundreds of thousands of Roma (Gypsies), homosexuals, disabled people, political dissidents and Soviet prisoners of war.