As Israel marks the 50th anniversary of the trial of Adolf Eichmann, new documents and witness accounts are coming to light in Germany that reveal more details about the postwar life of the Nazi war criminal right up to his capture by the Mossad.

Over the weekend, the German weekly Der Spiegel published a transcript of a tape recording in which Eichmann, who lived in Argentina after the war, can be heard bragging to his friends about his role in the Holocaust. Eichmann is even heard expressing regret for not being able to complete the task.

"We didn't do our work correctly," he said. "There was more that could have been done."

In the recording, Eichmann, who masterminded the expulsion and transfer of millions of Jews from their homes to the death camps, contradicts statements he later made in his defense during his 1961 trial in Jerusalem. Eichmann was found guilty and executed.

At his trial, Eichmann's attorneys claimed that he was a low-level cog in the Nazi system who simply followed orders. "It was not my desire to kill people," he said. "The mass murder is the fault of the political leaders only."

Yet Eichmann is heard on the tape saying: "I was no ordinary recipient of orders. If I had been one, I would have been a fool. Instead, I was part of the thought process. I was an idealist."

The conversation is purported to have taken place in a Buenos Aires suburb between Eichmann and two friends who were also former Nazis. The recording is being kept in the German Federal Archives.

The recording is one of thousands of testimonies that have been released in recent months as part of a media campaign urging German intelligence agencies to declassify more than 4,500 documents connected to the Eichmann case.

After the Holocaust, thousands of Nazis, including senior officials who held prominent positions in the killing apparatus, escaped to Argentina. Eichmann was one of them.

The newly revealed documents confirm that thousands of Germans, including people in the intelligence agencies, were aware of Eichmann's whereabouts as early as the 1950s. According to a memorandum by the German Embassy staff in Buenos Aires, at least 300 employees who worked alongside Eichmann in a factory knew the real identity of the man who lived under the name Ricardo Klement.

Eichmann, who reunited with his wife and children in Argentina, was a popular figure in the Nazi community that had found refuge in the country. He was known to have met Josef Mengele, the notorious Angel of Death who conducted experiments on inmates at Auschwitz, at a Buenos Aires coffee shop.

On another occasion, Eichmann attended a going-away party for Johann von Leers, an anti-Semitic polemicist and Nazi propagandist who fled to Egypt.

Another declassified dispatch revealed that Eichmann took part in a ceremony honoring Argentine army colonel Juan Peron, who would later become president. Peron was known to have helped a number of Nazis find shelter in Argentina.

Two of Eichmann's closest friends during his time in Argentina were pro-Nazi journalists. His circle later expanded to include an assistant to Heinrich Himmler, the former head of the SS and Gestapo.

German and other intelligence agencies monitored Eichmann's activities and received information on his whereabouts in the 1950s, yet they did not act to apprehend him.

Newly released documents from the German Foreign Ministry's archives also show that the German Embassy in Argentina even provided passports to Eichmann's children so they could visit Germany in 1954.