British best-selling author David Cornwell, better known as John le Carre whose Cold War-era spy novels transformed the espionage genre, died over the weekend, his literary agent said. He was 89 years old.

His family said le Carre died Saturday night in Cornwall, Britain, from pneumonia after a short battle with the illness.

Le Carre's literary career spanned nearly six decades and included 26 books, including The Spy Who Came in From the Cold, the 1963 novel that placed his name among the very best of the spy genre with his plump and balding spy, George Smiley, critiquing Ian Fleming's dapper and handsome James Bond.

His literary career began near the tail end of his time working for the British intelligence service. In the late 1950s, he spied on far-left groups seeking information on possible Russian agents before transferring to the foreign intelligence service, known as MI6, in the early 1960s, according to publishing house Penguin Random House Canada.

"From the day my novel was published, I realized that now and for ever more I was to be branded as the spy turned writer, rather than as a writer who, like scores of his kind, had done a stint in the secret world, and written about it," he wrote in a postscript to the novel. "The novel's merit, then -- or its offense, depending on where you stood -- was not that it was authentic, but that it was credible."

In the late 1950s, he spied on far-left groups seeking information on possible Russian agents before transferring to the foreign intelligence service, known as MI6, in the early 1960s, according to publishing house Penguin Random House Canada.

"From the day my novel was published, I realized that now and for ever more I was to be branded as the spy turned writer, rather than as a writer who, like scores of his kind, had done a stint in the secret world, and written about it," he wrote in a postscript to the novel. "The novel's merit, then -- or its offense, depending on where you stood -- was not that it was authentic, but that it was credible."

Along with The Spy Who Came in From the Cold, several of his novels have been turned into films, including Tinker Tailor Soldier Spy in 2011, which received three Oscar award nominations./World News