Oona Chaplin has been cast in 'Avatar' sequels.

Oona Chaplin

Oona Chaplin

The 'Game of Thrones' actress will play Varang, who is described as a strong, vibrant central character and is set to appear in all four upcoming sequels.

Oona, 31, will be work alongside a host of returning cast members, such as Zoe Saldana, Sam Worthington, and Sigourney Weaver, according to Empire.

The original 'Avatar' movie was released in 2009, and was a huge success with fans and critics.

But James Cameron recently defended the 11-year gap between the first 'Avatar' movie and the upcoming sequels.

The 62-year-old filmmaker announced earlier this year that the "concurrent production on four sequels" had begun and the first movie will be released in 2020, followed by the other three in 2021, 2024 and 2025.

Defending the gap between the original hit and the sequels, he said: "It was a seven year gap between 'The Terminator' and 'Terminator 2: Judgment Day', seven year gap between 'Alien' and 'Aliens'.

"It's going to be obviously more like a ten year gap between 'Avatar' and 'Avatar 2'.

"But 'Avatar 2' you are going to with not the promise but the certainty of three more films beyond that, and that's a very different concept with the audience. And a lot of the delay has been around creating that overall vision."