MUMBAI: James Cameron's planned Avatar movie trilogy is becoming a quadrilogy.

Josh Friedman (War of the Worlds), Shane Salerno (Savages) and Rick Jaffa and Amanda Silver (Rise of the Planets of the Apes) have been hired to collaborate with the director to write three follow-ups to Cameron's 2009 sci-fi blockbuster hit Avatar, 20th Century Fox announced last week.

The original currently stands as the USA's all-time box-office tyrant with a take of $760 million.

The first sequel to Avatar, which followed a space marine (Sam Worthington) going native with a race of blue alien Na'vi on the moon Pandora, will begin production next year and will film simultaneously with the two other sequels.

Avatar 2 is due out in December 2016, with Avatar 3 coming in December 2017 and Avatar 4 tentatively releasing December 2018.