Google's Boston Dynamics division has released footage of its Atlas humanoid robot taking a walk in a forest.

The 6ft 2in (1.9m) machine required a power tether to keep it charged, but was able to keep itself balanced despite the unpredictable terrain.

"Our focus is on balance and dynamics - working a little bit the way people and animals do, where you move quickly in order to keep yourself stabilised," explained Boston Dynamics' founder Marc Raibert to the Fab 11 conference earlier this month.

"Out in the world is just a totally different challenge than in the lab. You can't predict what it's going to be like.

"We're working on a version that doesn't have that [power tether] and we're making pretty good progress on making it so it has mobility that's within shooting range of [a human's]."

Boston Dynamics has shown off other models tackling similar outside courses in the past, but they had more legs to help them stay upright.

Earlier in the year, other versions of Atlas were entered into the Pentagon's Darpa Robotics Challenge - a contest that also involved navigating rough terrain - however, another model from South Korea took the top prize.