BEIJING - China and Japan engaged on Friday in a fresh round of invective over military movements near a disputed group of uninhabited islands, fueling tensions that for months have bedevilled relations between the two major Asian powers.China's defense ministry rejected a Japanese allegation that a naval vessel had aimed a weapons-targeting radar at a Japanese military ship in the East China Sea, its first comment on the week-old incident. It said Japan's intrusive tracking of Chinese vessels was the "root cause" of the renewed tension.A Japanese official on Friday dismissed the Chinese explanation for the Jan. 30 incident. He said Beijing's actions could precipitate a dangerous situation in waters around the islets, known as Diaoyu in China and Senkaku in Japan, believed to be rich in oil and gas.His comments came a day after Japan said two Russian fighter jets briefly entered its air space near other, long-disputed islands, prompting Japan to scramble combat fighters. Russia denied the charge.