Charmian Carr who played Liesl in hit 1965 film Sound of Music has died aged 73.

The American actress died in Los Angeles from complications from a rare form of dementia, her representative said.

The Rodgers and Hammerstein film, which quickly became the highest grossing film of all time, went on to become a cult classic and was reprised often on stage and TV.

Carr was born in 1942 in Chicago to an actress mother and musician father.

She sang the duet Sixteen going on Seventeen and was a college student when she auditioned.

It’s reported she hadn’t received any singing or dancing lessons prior to being cast.

After Sound of Music, Carr only featured in one other role – Stephen Sondheim’s television musical, Evening Primrose.

Carr later wrote two books on her experience, Forever Liesl and Letters to Liesl, and often attended events to commemorate the film.

In a 2005 interview, she said that people should consider singing along to Sound of Music as “like going to therapist”.

“It’s just a kind of therapy,” she said.

“They can move around. They can dance and talk back to the screen. They can skip their appointment with the shrink that week.”

Shortly after the announcement, many fans took to Twitter to express their condolences.

Kym Karath, who played youngest daughter Gretl, said: “She has been like a sister throughout my life.”

Ted Chapin, president of the Rodgers and Hammerstein organisation, said: “It’s always sad when a member of the family passes away and in the case of the ‘family’ of the movie The Sound of Music, it’s especially sad when it is the first of the group to go.”

The real life Liesl, Agathe von Trapp, who was the oldest daughter of the Austrian family that inspired the film passed away in 2010 aged 97.

Watch her performance in the film below