Tokyo - A shell, possibly left from World War II, exploded early Wednesday on the southern Japanese island of Okinawa, inflicting serious injury to a construction worker, media reports said.

Police were quoted as saying Jun Kohagura suffered injuries on his face when the shell, believed to have been a dud fired or dropped from an aircraft during the war, exploded. A 75-year-old man laying bed at a nearby senior home also suffered minor injury to his heels from windows that broke as a result of the blast.

The shell was buried at about a metre deep, and it detonated when Kohagura was digging with heavy machinery for water-pipe construction project in Itoman City.

Neighbous heard a loud blast and saw smoke rising from the site, media reports said.

A number of duds have been discovered in Itoman, the scene of one of the fiercest battle between Japanese and US troops in the closing days of WWII. (dpa)