The ball was discovered by a local resident, who called the police at about 08.45 local time on Tuesday (23:45 GMT on Monday), a Japanese broadcaster reported.
The traffic in the area is being strictly regulated. The object is currently being checked by specialists who have arrived at the scene, according to the news outlet. Moreover, photos of the balloon have been sent to the Japan Self-Defense Force and the Coast Guard, the report said.
No further information on the incident has been provided so far.
Later in the day, representatives of the Omaezaki branch of the Japanese Coast Guard told Sputnik they did not yet know what the large metal ball was.