A four-legged robot called BigDog sporting an arm powerful enough to lift and throw cinder blocks could be used in search and rescue, a U.S. robotics firm says.

BigDog, by U.S. robotics firm Boston Dynamics, was funded by the Pentagon and is designed primarily for military use, with a powerful arm that can pick up and carry heavy loads for soldiers.

In a company video the robot is featured lifting a cinder block with an arm and then flinging it backwards.

The robot can move over rugged terrain while carrying a load, perform simple tasks and obey voice commands.

Chris Melhuish, director of Bristol Robotics Laboratory, called it a "a phenomenal piece of technology."

Its ability to follow a person and obey commands made it "an interesting navigation machine which might end up useful in other domain, such as search and rescue," he told the BBC.

"[Imagine] setting off these units across a rough terrain if they were looking for a lost child or a walker on a mountainside," he said.