Chinese ships patrol disputed islands

• Tensions between Japan and China are high over a group of disputed islands
• Japan controls the islands, but China claims they are part of its territory

(CNN) -- Two fleets of Chinese maritime surveillance ships entered waters around a group of islands at the center of a heated territorial dispute between Tokyo and Beijing, Chinese state media reported Friday, intensifying tensions in the region.

The six Chinese ships arrived near the uninhabited islands -- which Japan calls Senkaku and China calls Diaoyu -- on Friday morning and began patrols and "law enforcement," China's state-run news agency Xinhua reported, citing a government statement.

The islands, situated in the East China Sea between Okinawa and Taiwan, are currently under Japanese control, but China claims they have been an "inherent" part of its territory "since ancient times."

The Chinese move to begin patrols around the islands follows the Japanese government's purchase of several of the islands from a private Japanese owner earlier this week, a deal that China described as "illegal and invalid."