Two sharks have been spotted off the coast of Hokota in Ibaraki Prefecture, prompting authorities in the city and in three municipalities nearby to prohibit swimming in the sea on Wednesday.

According to the Ibaraki Prefectural Government, the city of Hokota received the reports from residents starting Tuesday night and the Ibaraki Coast Guard Office on Wednesday spotted two sharks, one about 4 meters long. They're believed to be sand sharks.

The prefectural 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.

Swimming was prohibited at beaches in the cities of Hokota, Kashima, Kamisu and the town of Oarai on Wednesday. Hokota, Kashima and Oarai plan to continue the ban on Thursday.