Actor Leonard Nimoy, who won a worldwide fan base as the pointy-eared half-human, half-Vulcan Mr Spock in the Star Trek television and film franchise, has died at age 83.

Nimoy, who suffered from chronic obstructive pulmonary disease, died at his home in Los Angeles.

His wife, Susan Bay Nimoy, confirmed the death to the New York Times. A private memorial service was being planned.

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An outpouring of grief on social media has paid tribute to the man considered by many to be a geek idol.

Nimoy's Star Trek co-star William Shatner, who played hot-headed Captain James T Kirk, said he would miss the man he loved "like a brother".

"We will all miss his humour, his talent, and his capacity to love," Shatner said on Twitter.

Fellow co-star George Takei, who played Mr Sulu, posted his heartfelt tribute to Facebook.

"Today, the world lost a great man, and I lost a great friend," Takei posted to his public Facebook page.

Sorry, this video has expired Michael Vincent talks to News 24 about Leonard Nimoy's legacy

"We return you now to the stars, Leonard. You taught us to 'live long and prosper', and you indeed did, friend. I shall miss you in so many, many ways."

Nimoy began his acting career at the age of 18, winning a sprinkling of small parts in 1950s television series, before landing the iconic role of Mr Spock in Star Trek in 1966.

Aboard the spaceship USS Enterprise, science officer Spock and his crew ventured around the galaxy exploring new worlds in death-defying odysseys.

The character Spock would be resurrected for several feature films after Star Trek snowballed into a cultural phenomenon in the 1970s and 1980s, making Spock's Vulcan salute and salutation "live long and prosper" a touchstone of the science-fiction world.

Nimoy would later reveal he based the hand gesture on a Jewish blessing.

US president Barack Obama said he "loved Spock".

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"Long before being nerdy was cool, there was Leonard Nimoy," Mr Obama said.

"In 2007, I had the chance to meet Leonard in person. It was only logical to greet him with the Vulcan salute, the universal sign for 'live long and prosper'.

"And after 83 years on this planet – and on his visits to many others – it's clear Leonard Nimoy did just that."

In addition to acting, Nimoy was an accomplished director, directing two of the Star Trek films and 1987 box-office hit Three Men and a Baby starring Tom Selleck.

Last year, he disclosed on Twitter that he had been diagnosed with COPD, a progressive lung disease.

"I quit smoking 30 years ago. Not soon enough," he tweeted to his 810,000 followers. "Grandpa says, quit now!!"

A geek role model

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In the minds of avid Star Trek fans, known as Trekkies, Nimoy and Spock were inseparable.

In 1975, he authored the book I Am Not Spock, attempting to open up space between himself and the character that had so captured people's imaginations.

But he would eventually embrace his role as an authority figure in the sci-fi world, writing a rebuttal to his earlier memoir in I Am Spock in 1995.

Leonard Nimoy gives the Vulcan salute, his invented gesture that has become a symbol for Star Trek fans everywhere. ( Reuters: Fred Prouser )

As Spock, Nimoy became a role model for nerds and geeks. He was calm under pressure with a logical response always at the ready.

He related an "embarrassing" anecdote to The New York Times in 2009 where he toured a California university with scientists who looked to Spock for approval.

"Then they'd say to me, 'what do you think?' expecting me to have some very sound advice. And I would nod very quietly and very sagely I would say, 'you're on the right track'," he said about his adulation in the science community.

Nimoy had two children with his first wife, and was married to his second wife Susan since 1989.

Nimoy built off his sci-fi and Spock fame for the rest of his career, lending his voice to documentaries, video games and television shows.

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He sold "Live Long and Prosper" apparel, and waved the Vulcan salute at Star Trek conventions.

He returned to Star Trek as an older version of his Spock character in the franchise's reboot directed by JJ Abrams in 2009 and in a 2013 sequel.

Nimoy remained active in his later years, releasing photography books and poetry.

He also took a role on sci-fi TV series Fringe, which ran from 2008 to 2013 and was also directed by Abrams.

In his last tweet, posted Monday under his handle @TheRealNimoy, Nimoy said: "A life is like a garden. Perfect moments can be had, but not preserved, except in memory."

Zachary Quinto, who played Spock in the two most recent Star Trek films, said he was heartbroken.

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"I love you profoundly my dear friend and I will miss you everyday," he said on Instagram, alongside a portrait of Nimoy.

"Today we salute the legendary Leonard Nimoy #LiveLongAndProsper," tweeted the nerdy hit CBS sitcom The Big Bang Theory, on which Nimoy once made a memorable cameo appearance voicing a Spock doll.

In the heart of Hollywood on Friday, fans paid tribute to Nimoy at his star on the Walk of Fame.

"Before Obi-Wan, before Yoda, before Star Wars - there was Spock," said Gregg Donovan, an English-born actor dressed in a top hat, a red tailcoat and white gloves, who said he once bagged Nimoy's groceries at a Los Angeles supermarket.

"I always remember his kindness. I told him I was a member of the Screen Actors Guild and he said, 'Keep going, don't give up'."

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ABC/AFP