BEIJING – Chinese patrol boats have harried the Japanese Coast Guard many times a week for more than a month in an unusually relentless response to their latest maritime spat.

Four Chinese craft typically push to within hailing distance of Japan’s ships. They flash illuminated signs in Japanese to press Beijing’s argument that it has ancient claims to a set of tiny East China Sea islands now controlled by Tokyo.

China said its craft have tried to chase the Japanese away at least once, although Japan denies any of its ships fled.