McCallum died on Monday of natural causes surrounded by his family at New York Presbyterian Hospital, TV network CBS said in a statement.

"David was a gifted actor and author, and beloved by many around the world. He led an incredible life, and his legacy will forever live on through his family and the countless hours on film and television that will never go away," the network said.

"We will miss his warmth and endearing sense of humour that lit up any room or sound stage he stepped onto, as well as the brilliant stories he often shared from a life well-lived."

A previously announced 20th-anniversary NCIS marathon on Monday night (US time) will now include an "in memoriam" card in remembrance of McCallum, the network said.

Music, theatre and success in films, TV:

Born in Glasgow in 1933, McCallum grew up with musical parents. When he was three years old his family moved to London, where his father played with the London Philharmonic and Royal Philharmonic.

He attended the Royal Academy of Music, where he studied the oboe but soon decided he wasn't good enough to be a professional musician.

He then turned to theatre, studying briefly at the Royal Academy of Dramatic Art.

"I was a small, emaciated blond with a caved chest, so there weren't an awful lot of parts for me," he commented in a Los Angeles Times interview in 2009.

After time out for military service, he returned to London and began getting work on live television and movies.

In 1957 he appeared in Robbery Under Arms, an adventure set in early Australia, with a rising actress, Jill Ireland. The couple married that same year.

In 1963, McCallum was part of the large cast of The Great Escape, and he and his wife became friendly with Charles Bronson, who also appeared in the film.

Ireland eventually fell in love with Bronson, and she and McCallum divorced in 1967. She married Bronson in 1968.

"It all worked out fine," McCallum said in 2009, "because soon after that I got together with Katherine [Carpenter, a former model] and we've been very happily married for 42 years."

While he had some moderate success in films, it was 'The Man From U.N.C.L.E.' that made the blond actor with the Beatle-esque haircut a household name in the mid-1960s.

The success of the James Bond books and films had set off a chain reaction, with secret agents proliferating on both large and small screens.

Indeed, Bond creator Ian Fleming contributed some ideas to The Man From U.N.C.L.E. as it was being developed, according to Jon Heitland's The Man From U.N.C.L.E. Book.

The show, which debuted in 1964, starred Robert Vaughn as Napoleon Solo, an agent in a secretive, high-tech squad of crime fighters whose initials stood for United Network Command for Law and Enforcement.

Despite the Cold War, the agency had an international staff, with McCallum playing Illya Kuryakin, Solo's Russian sidekick.

The role was relatively small at first, McCallum recalled, adding in a 1998 interview that "I'd never heard of the word 'sidekick' before".

The show drew mixed reviews but eventually caught on, particularly with teenage girls attracted by McCallum's good looks and enigmatic, intellectual character.

By 1965, Illya was a full partner to Vaughn's character and both stars were mobbed during personal appearances.

McCallum's work with U.N.C.L.E. brought him two Emmy nominations, and he got a third as an educator struggling with alcoholism in a 1969 Hallmark Hall of Fame drama called Teacher, Teacher.

NCIS role marked a return to fame:

40 years later ... McCallum returned to television in 2003 to star in another series with an agency known by its initials — CBS's 'NCIS'.

He played Dr Donald "Ducky" Mallard, a bookish pathologist for the Naval Criminal Investigation Service, an agency handling crimes involving the navy or the marines. Mark Harmon played the NCIS boss.

McCallum said he thought Ducky, who sported glasses and a bow tie and had an eye for pretty women, "looked a little silly, but it was great fun to do".

He took the role seriously, too, spending time in the Los Angeles coroner's office to gain insight into how autopsies are conducted.

The series built an audience gradually, eventually reaching the roster of top 10 shows.

McCallum, who lived in New York, stayed in a one-bedroom apartment in Santa Monica when NCIS was in production.

While working on the series in 2007, McCallum told a reporter:

"I've always felt the harder I work, the luckier I get. I believe in serendipitous things happening, but at the same time, dedicating yourself to what you do is the best way to get along in this life."

McCallum had three sons from his first marriage, Paul, Jason and Valentine, and a son and daughter from his second, Peter and Sophie.

"He was a true Renaissance man — he was fascinated by science and culture and would turn those passions into knowledge," Peter McCallum said in a statement.

"For example, he was capable of conducting a symphony orchestra and (if needed) could actually perform an autopsy, based on his decades-long studies for his role on NCIS."

Souce | AP