Over 67 years since he disappeared into the Soviet prison system, the fate of the Swedish diplomat Raoul Wallenberg remains veiled in mystery despite decades of work to find the truth.

Had he lived, Wallenberg – who saved thousands of Jews from their deaths

in Nazi-occupied Hungary in World War II – could have been celebrating his 100th birthday on August 4th.

But he was arrested by the Soviet Union in Hungary in January 1945, sent to Moscow and, according to the official Russian account, died in prison in the Soviet capital in 1947.

Yet no document has ever emerged confirming Wallenberg died that year, and reported sightings across the Soviet prison system that lasted up to the 1980s gave rise to the tantalising possibility he could still be alive.

The last time Wallenberg was seen alive for certain was January 1945, when he told colleagues in Budapest he was heading to Debrecen to meet the advancing Red Army along with his driver Vilmos Langfelder.

Wallenberg was arrested by Soviet counter-intelligence agency SMERSH on the orders of the deputy Soviet defence commissar Nikolai Bulganin, who signed the arrest warrant.

Why he was arrested is another mystery, although some historians point to Wallenberg’s links with the CIA and previous working contacts with Nazi officials.

He was taken to Moscow by train, but thereafter only the faintest scraps of verifiable and publicly available documents exist on his fate.

The possibility that Moscow could still be concealing the key documents confirming he was murdered by Josef Stalin’s secret police has long angered historians in Sweden and Russia and prolonged the agony for his family.

“This is still a painful topic for Russia. But the fact is that Wallenberg was killed,” said Nikita Petrov, the deputy director of the Memorial group which fights for historical memory in Russia.

“The present Russian leadership does not want to reveal the documents, but that they exist cannot be disputed,” he told Voice of Russia radio station ahead of the birthday anniversary.

“Wallenberg’s fate is known. But admitting that he was killed is something that Russia seems unable to do. Documents exist and Russia must release them to close the case.”

‘We regret this profoundly’

Official explanations about Wallenberg’s disappearance started with a bare-faced lie: Soviet-controlled Hungarian radio said he had been killed by pro-Nazis on his way to Debrecen.

The USSR then confirmed to Stockholm that Wallenberg was alive and in Moscow. But after that the trail went cold for years.

In the so-called “thaw” under Stalin’s successor Nikita Khrushchev, the USSR in 1957 released a document signed by Smoltsov (no first name), the head of the prison infirmary at the Lubyanka, the notorious building where the KGB security services were headquartered.

Kept secret for 10 years, the document said Wallenberg had died of heart failure on July 17th, 1947 in the Lubyanka. Smoltsov was no longer around to explain more – he had died in 1953.

Amid scepticism in Sweden over this conclusion, special commissions were opened in Russia just before the collapse of the Soviet Union and afterwards.

In 2000, the head of a Russian commission of investigation, Alexander Yakovlev, said that Wallenberg had been killed in the Lubyanka, but no document ever surfaced to back this up.

In December 2000 Russia took the historic step of declaring Wallenberg and Langfelder victims of political repression – even though officially they were never convicted of a crime.

“Raoul Wallenberg and Vilmos Langfelder died in our country,” Nikolai Patrushev, then-chief of the FSB (the former KGB) and current head of Russia’s national security council, said at a “rehabilitation” ceremony on January 19th, 2001.

“There is no doubt that Wallenberg and Langfelder were arrested illegally and for political reasons and we regret this profoundly,” he said. But no explanation for his death was forthcoming.

Reported sightings of Wallenberg were most concentrated around the prison of Vladimir east of Moscow in the 1950s. But he was also “seen” farther a field in the GULAG in Siberia and the Far East.

Two historians who worked on the investigative commissions said in 2010 that the FSB had essentially confirmed that Wallenberg did not die on July 17, 1947, undermining the credibility of the medical document.

Historians Susanne Berger and Vadim Birstein said the FSB archivists had informed them that Wallenberg was “Prisoner number 7” who according to documents was interrogated on July 23rd, 1947.

The head of the FSB’s archives section, Valery Khristoforov, has repeatedly stated that the Wallenberg case is open, but has also vehemently denied that the organization has concealed documents.

Memorials to Wallenberg’s heroism exist all over the world and also in Moscow. But the small bust in the courtyard of the Rudomino foreign languages library goes unnoticed by most residents of the Russian capital.