Anti-Japan protests rage in China. Angry over the Japan's purchase of disputed islands in the East China Sea, demonstrators hurl water bottles at the Japanese embassy in Beijing. Japan bought the uninhabited islands last week from a private Japanese owner, increasing tension between the two nations. On the anniversary of Tokyo's 1931 invasion of China, protesters also march outside the embassy in Shanghai. In Beijing Tuesday to promote bilateral ties, U.S. Defense Secretary Leon Panetta urged restraint. SOUNDBITE (English) LEON PANETTA, UNITED STATES DEFENSE SECRETARY, SAYING: "We have always tried to advance the security of the entire region, going all the way back to World War II. And so our purpose in being able to strengthen our presence in this region is to promote greater prosperity, to promote greater security in the Asia Pacific region." Meanwhile Japanese activists rallied in Tokyo. The islands have potentially huge oil and gas reserves - of interest to both countries.