Jonathan Lloyd, his agent, said Forsyth died at home early on Monday surrounded by his family.

“We mourn the passing of one of the world’s greatest thriller writers,” Lloyd said.

Born in Kent, in southern England, in 1938, Forsyth served as a Royal Air Force pilot before becoming a foreign correspondent.

His experience covering the 1962 assassination attempt on French President Charles de Gaulle inspired his popular political thriller, The Day of the Jackal, which centers on a professional assassin.

Published in 1971, the book propelled him into global fame.

It was made into a film in 1973 starring Edward Fox as the Jackal and more recently a television series starring Eddie Redmayne and Lashana Lynch.

In an interview with the BBC in 2015, Forsyth revealed his long-term involvement with the British intelligence agency MI6, beginning during his reporting of a civil war in Nigeria in the 1960s.

Although Forsyth said he did other jobs for the agency, he said he was not paid for his services and “it was hard to say no” to officials seeking information.

“The zeitgeist was different,” he told the BBC.

“The Cold War was very much on.”

He wrote more than 25 books including The Afghan, The Kill List, The Dogs of War and The Fist of God that have sold over 75 million copies, Lloyd said.

His publisher, Bill Scott-Kerr, said that Revenge of Odessa, a sequel to the 1974 book The Odessa File that Forsyth worked on with fellow thriller author Tony Kent, will be published in August.

“Still read by millions across the world, Freddie’s thrillers define the genre and are still the benchmark to which contemporary writers aspire,” Scott-Kerr said.