James Cameron’s sci-fi opus “Avatar” became the fastest-selling home entertainment release in North American history, selling a combined total of 6.7 million DVDs and Blu-rays in just four days, IGN reported Monday.

The Oscar-winning movie, symbolically released in the U.S. on April 22 — Earth Day — sold approximately four million DVDs and 2.7 million Blu-rays, grossing around $130 million.

It therefore smashed the Blu-ray record held by “The Dark Knight,” which took 18 months to sell 2.5 million copies — although it should be noted that the platform had much less market penetration at the time.

That’s on top of the sci-fi epic’s $2.7 billion cinematic gross, which made it the most successful film in history.

And with the film hitting shelves outside the U.S. on Monday and also receiving a theatrical re-release in the summer, it looks like the title will continue to generate cash throughout 2010.

“Avatar” was produced by Twentieth Century Fox, a subsidiary of News Corp., which also owns NewsCore.