American actress Nichelle Nichols, best known for her role in 1960s sci-fi TV series Star Trek, has died aged 89.

Nichols broke barriers in her role as Lieutenant Nyota Uhura in the series, becoming one of the first black actresses in the US to play a figure in authority.

She was later employed by Nasa in an effort to encourage more women and African-Americans to become astronauts.

She died of natural causes on Saturday night, her son Kyle Johnson said.

In a statement posted on Facebook, Mr Johnson wrote: "I regret to inform you that a great light in the firmament no longer shines for us as it has for so many years.

"Her light however, like the ancient galaxies now being seen for the first time, will remain for us and future generations to enjoy, learn from, and draw inspiration."

US President Joe Biden paid tribute, saying: "In Nichelle Nichols, our nation has lost a trailblazer of stage and screen who redefined what is possible for Black Americans and women."

The Star Trek TV series broke down stereotypes in the 1960s by casting black and minority actors in high-profile roles.

Nicholls was cast in the series as Lt Uhura, who was portrayed as a competent and level-headed communications officer - shattering stereotypes.

In 1968, she and Star Trek star William Shatner, who played Captain Kirk in the series, broke new ground when they shared one of television's first interracial kisses - though it was not a romantic one.

Despite her success, however, Nichols had initially considered leaving the show. But she was convinced otherwise by Dr. Martin Luther King Jr., who described her character as the "first non-stereotypical role portrayed by a black woman in television history".

She wanted to leave because she had been offered a role in a show that was heading to Broadway,saying in an interview that her "life was theatre".

Nichols was asked by Star Trek creator Gene Rodenberry to think about her decision for a couple of days, which she agreed to do.

That weekend, she went to a fundraiser in Los Angeles where she was introduced to someone who was described by the event organiser as "her biggest fan, he's desperate to meet you".

That man was Dr. Martin Luther King Jr. who said: "Yes, Miss Nichols, I am your greatest fan. We admire you greatly."

She told him she was going to leave Star Trek and he said: "You cannot. You cannot. For the first time on television, we are being seen as we should be seen every day, as intelligent... beautiful, people who can sing, dance and go into space, be lawyers, teachers, and yet you don't see it on television until now."

Nichols explained: "I could say nothing, I just stood there realising that everything he said was the truth."

Dr. King continued: "Gene Rodenberry opened a door for the world to see us. If you leave, that door can be closed because your role is not a black role and it's not a female role, he can fill it with anyone, including an alien!"

Nichols later said: "At that moment, the world tilted for me and I knew then... that I was something else. The world was not the same. And I remember being angry - why me? Why should I have to?"

But she went back to Rodenberry the following week and told him what happened and said she would stay.

Rodenberry responded: "Thank god for Martin Luther King, somebody knows where I am coming from."

Nichols said she never looked back and had never regretted her decision.

She went on to feature in the first six Star Trek movies following the series' end in 1969.

As well as working as an actress, Ms Nicholls also became an ambassador for the US space agency Nasa, helping to recruit women and minorities to its Space programme.

Following the news of her death, Star Trek co-star George Takei wrote in a tweet: "My heart is heavy, my eyes shining like the stars you now rest among, my dearest friend."

"The importance of Nichelle's legacy cannot be over-emphasised. She was much loved and will be missed," said TV director Adam Nimoy - the son of Star Trek actor Leonard Nimoy.

Shatner also paid tribute.

"She was a beautiful woman and played an admirable character that did so much for redefining social issues both here in the US and throughout the world," he wrote on Twitter.

Marina Sirtis, who portrayed Counsellor Deanna Troi in Star Trek: The Next Generation and its four feature film adaptations, wrote that Nichols "opened the door for the rest of us who followed in your wake".

Nasa described Nicholls as a "trailblazer" and "role model".

J.J. Abrams, who was behind the 2009 Star Trek reboot and its 2013 follow-up Star Trek Into Darkness, called Nichols "a remarkable woman in a remarkable role."

British actress Adjoa Andoh wrote: "We stand on shoulders of groundbreaking greats. Nichelle Nichols you gave so many of us hope. Thank you."