Recent sightings of sharks off beaches in Ibaraki Prefecture have put local authorities on alert, but they have also been spotted in Shizuoka as well, raising safety concerns in the midst of the swimming season.
The most recent sharks spotted are all believed to be hammerheads.
According to Ibaraki prefectural officials, a hammerhead shark about 2 meters long was spotted about 200 meters off the port of Kashima on Monday, prompting local authorities to close two beaches nearby.
In Shizuoka, two other hammerhead sharks were found about 2 km off Yaizu Sunday, forcing a beach nearby to be closed starting Monday.
In Ibaraki last week, two sand sharks were spotted off the coast of Hokota, prompting authorities in the city and in three municipalities nearby to prohibit swimming in the sea.
The officials warn that the sharks could attack humans if provoked and are urging people not to go near them. It is rare for sharks to be seen close to the shore off Ibaraki, they said.