LOS ANGELES, USA: Four days after its release on DVD, 'Avatar' is on track to become as big a movie phenomenon in home entertainment as it was in theaters.

Twentieth Century Fox Home Entertainment said on Sunday that it sold 6.7 million DVD and Blu-ray units of the film in in the United States and Canada since the discs were released on Thursday.

That amounts to gross sales of $130 million, making the film from the studio division of News Corp. the No. 1 home entertainment opening ever over a four-day period.

The previous record holder for a similar stretch had been "The Dark Knight," which came out in 2008.

Fox said 2.7 million of its disc sales for "Avatar" came on Blu-ray, which is a newer technology that has a higher image quality than DVD but requires its own special player.

Director James Cameron's 3-D fantasy adventure become the No. 1 film ever at worldwide box offices after opening on Dec. 18. 'Avatar' made $2.7 billion, and beat the record set by Cameron's 1997 'Titanic.'

The film is about a soldier who infiltrates a tribe of space aliens on a distant moon, falls in love with a princess from the tribe and leads a rebellion against the human invaders who sent him on the mission.

Fox released the film on DVD and Blu-ray on Thursday to coincide with Earth Day, saying the timing dovetailed with 'Avatar's' theme of guarding the environment.