Robot wars: US smashes Japan in giant days-long duel

In scenes reminiscent of films like Transformers, a giant US robot fighting machine swung a "chainsaw sword" to chop a Japanese opponent into submission in a battle watched by tens of thousands online.

The two massive and heavily armed machines went claw-to-claw at an abandoned steel mill in Japan, firing cannons and smashing each other in a days-long duel.