British master spy Kim Philby, whose 30 years of treachery as a Soviet double agent haunted Western intelligence at the height of the Cold War, has died in the Soviet Union.

A Foreign Office spokesman said on Wednesday that word of his death at the age of 76 had come from the Soviet embassy in London. No details were given.A diplomat and journalist, he used his upper class background and good social and political connections in the British establishment to trade in treason. The secrets he passed to Moscow probably sent hundreds of British agents to their deaths.

Philby fled to Moscow in 1963 after years of leading British anti-Soviet espionage operations and meeting with U.S. Intelligence - all the time betraying secrets.

His exposure as one of the most successful agents of the Soviet KGB caused a scandal in Britain and for years soured relations with the CIA.

The Times of London quoted one former intelligence agent who knew Philby as saying, "I will have to open a bottle of champagne."

Philby was the "Third Man" in a ring of former Cambridge University graduates recruited to Soviet intelligence in the early 1930s.

When his accomplices, Foreign Office diplomats Guy Burgess and Donald Maclean, fled to Moscow in 1951 he was just a step away from becoming "C" - the supreme head of intelligence operations. But the defections threw suspicion on Philby.

He said in an interview with British journalist Philip Knightley that it was "that bloody man Burgess" who robbed him of his greatest prize by defecting.

After the Burgess-Maclean Affair he worked as a journalist and finally fled to Moscow from Beirut as the evidence piled up against him.

In the Soviet Union he was hailed as a hero and made a KGB general. His value to to the Soviet secret service was immense, and he said earlier this year he was still employed by the KGB.

He listened to cricket commentaries on British radio and yearned only for a few delicacies from home, such as marmalade and strawberry jam. He never tried to return.

Philby lived with his Russian wife Rufa in Moscow and enjoyed the privileges of a dacha, or country house. Unlike Burgess, he remained active in the KGB and never sought the company of Westerners.

"I want to be buried in the Soviet Union, in this country which I have considered to be my own ever since the 1930s," he told Knightley in a rare interview.

Maclean's remains were buried in a churchyard in a southern English village in 1983. Burgess, a flamboyant homosexual who drank heavily after his defection to Moscow and never came to terms with Soviet life, died 20 years ago of cancer.

Philby, Burgess and Maclean, as well as "Fourth Man" Anthony Blunt, who was publicly exposed as a spy in the early 1980s, were all members of a Cambridge university group.

Philby's cause of death is not known. But he goes to his grave carrying one last secret - who tipped him off in Beirut that he was about to be unmasked?