Simon Wiesenthal, a Holocaust survivor who spent much of his life hunting down Nazi war criminals, died Tuesday in the Austrian capital of Vienna at the age of 96.

Wiesenthal died in his sleep at his home, said Rabbi Marvin Hier, dean and founder of the Simon Wiesenthal Center in Los Angeles.

"Simon Wiesenthal was the conscience of the Holocaust," Hier said. "When the Holocaust ended in 1945 and the whole world went home to forget, he alone remained behind to remember. He did not forget.

"He became the permanent representative of the victims, determined to bring the perpetrators of the history's greatest crime to justice."

Wiesenthal is credited with bringing to justice more than 1,100 Nazi war criminals. They include Adolf Eichmann, one of Hitler's chief henchmen, and the policeman who arrested Anne Frank.

Between 1933 and 1945, the Nazis are believed to have killed at least 11 million civilians including six million Jews in central and eastern Europe.

When asked why he chose to track down Nazis who had escaped trial, Wiesenthal said: "When history looks back, I want people to know the Nazis weren't able to kill millions of people and get away with it."

The Israeli Foreign Ministry said Wiesenthal "brought justice to those who had escaped justice.''

"He acted on behalf of six million people who could no longer defend themselves,'' ministry spokesman Mark Regev said Tuesday.

B'nai Brith Canada said Wiesenthal was "a true hero of our times."

"He was a tireless fighter, who dedicated his life to seeking out Nazi war criminals and bringing to justice those who had committed the worst possible crimes against humanity," said Gerry Weinstein, B'nai Brith Canada's National President.

"A Holocaust survivor himself, Wiesenthal understood with his every breath that true justice allowed for no excuses, and no statute of limitations for Nazi war crimes."

Hunting Nazis

Wiesenthal was 33 when he was sent to a concentration camp in 1941, outside Lvov, Ukraine. Over the next four and a half years, Wiesenthal would be sent to several death camps before being liberated. Though he survived, some 89 of his relatives were killed by Nazis.

Wiesenthal's quest began in 1945. Instead of returning to his profession as an engineer, Wiesenthal stayed in Vienna and dedicated his life to finding Nazi war criminals.

In the 1950s, he helped track down Eichmann in Argentina, though some dispute his role in that capture. Eichmann was later kidnapped by the Israelis, tried for crimes against humanity, convicted and hanged.

He also decided to pursue Austrian policeman Karl Silberbauer in 1958. Silberbauer is believed to have arrested Dutch teenager Anne Frank. She was sent to the Bergen-Belsen concentration camp, where she died just days before it was liberated.

Two of his main targets were never captured: Josef Mengele, the infamous "Angel of Death" of the Auschwitz concentration camp, who died in South America after eluding capture for decades.

Former SS Colonel Walter Rauff was also never brought to justice. Rauff died of cancer at the age of 77 in Chile in May 1984.

A memorial service for Wiesenthal is planned for Wednesday in Vienna's central cemetery. Funeral services will be held in Israel, where he will also be buried.

Wiesenthal was married in 1936 to Cyla Mueller. She died in November, 2003.

The Wiesenthal Center has 1,200 open cases of Nazi war criminals it believes are still alive and living in 15 countries, including: Austria, Ukraine and Croatia.