Japan has strongly protested after Chinese J-15 fighter jets locked their radars on Japanese aircraft twice on Saturday near the southern Okinawa islands. Locking radar on a plane is seen as a threat and could mean a potential attack. Japan scrambled its fighter jets in response. China claimed Japan was "harassing" its forces during a training exercise. No one was hurt and no damage occurred. Tensions between Japan and China have worsened since Japanese Prime Minister Sanae Takaichi hinted Tokyo might act militarily if China attacks Taiwan. China claims Taiwan as its territory and has not ruled out force. Both countries have exchanged harsh words recently, affecting citizens on both sides. Japan's defence official said the Chinese jets' purpose was "unclear" but noted that "there was no need" to lock radar if they just wanted to locate planes. The radar locks happened at 16:32 and again at 18:37 local time. The Japanese jets did nothing provocative. Prime Minister Takaichi called the incidents "extremely regrettable" and said Japan "firmly requested measures to prevent recurrence." She promised Japan "will respond calmly and resolutely." China's navy rejected Japan's claims as "completely inconsistent with the facts" and told Tokyo to "immediately stop slandering and smearing." It added its training had been pre-announced. This episode follows a recent scramble of Japanese jets over a suspected Chinese drone near Yonaguni island, near Taiwan. Japan plans to deploy missiles on Yonaguni, angering Beijing. In the past month, China has urged citizens to avoid Japan, banned Japanese seafood imports, and stopped screening popular Japanese films as the fight spills over beyond military lines.