A humanoid robot named "Robovie-PC" (R) leads in a race against other robots during the world's first full-length marathon for two-legged robots, in Osaka.

The world's first full-length marathon for two-legged robots kicked off in Japan on Thursday, with the toy-sized humanoids were due to run 42.195 kilometres (26 miles) over four days.

The machines began the non-stop race on a 100-metre (109-yard) indoor track in the western city of Osaka after doing knee bends or raising their hands to greet spectators.

The bipedal robots -- the tallest of which measures 44 centimetres (17.6 inches) -- must complete 423 laps to reach their goal.

The "Robo Mara Full" race is organised by Vstone Co., a technology firm based in the western industrial city, in cooperation with the Osaka prefectural government.

Competitors are allowed to change batteries and the so-called servomotors which control the robots' speed and other functions.

Robovie-PC from Vstone led the race at the start. Video footage from a camera in its head can be seen at http://www.ustream.tv/channel/robovie-pc.

A wide view of the race can be seen live at here.

(c) 2011 AFP