The first 10 minutes of Disney's ambitious John Carter have been released online.

The £250m adaptation of Edgar Rice Burrough's science fiction novels sees a Confederate captain transported to the red planet, where he becomes embroiled in war games between rival factions.

Concerns have been raised in Hollywood that the film's niche subject matter will see takings fall short of its enormous budget. The footage, screened by MovieClips, shows the character on Earth as the film opens.

The film is released on March 6.