TOKYO — Police are increasing security for the Casio World Open after a caller warned that mines had been buried at the venue and small explosions shattered windows at the clubhouse and building of a corporate sponsor.

Police said they will deploy around 160 officers at the Kuroshio Country Club in Kochi, where the four-day Japan Golf Tour event will kick off Thursday. They will also guard hotels where players will stay for the tournament about 390 miles southwest of Tokyo.

The police deployment will begin on Wednesday after an anonymous caller told a local newspaper Tuesday and said he had buried mines at the tournament venue.

The man demanded the golf tournament be canceled, police said. Police checked the venue for about two hours following the call but found nothing.

The call follows small explosions last week at the clubhouse and building of a corporate sponsor in Kochi. No one was injured in the explosions, which occurred late at night. Police declined to give details on the explosions.

The Mainichi daily reported Tuesday that hand grenades were the likely cause of the blasts.

Japan Golf Tour officials could not be reached for comment late Tuesday.