Japanese nationalists have upped the ante in a territorial dispute with China by landing on a group of islands in the East China Sea and hoisting flags, in defiance of a government ban.

News reports said the 150 nationalists, including several local government councillors, arrived on a 20-strong flotilla of boats waving Japanese flags. "The Senkakus are undoubtedly Japanese territory," a Tokyo politician, Eiji Kosaka, told the Associated Press.

Tokyo deported a group of Hong Kong activists who waded ashore to the islands last week on the 67th anniversary of Japan's surrender in the Second World War, carrying Chinese and Taiwanese flags. The men returned home to a hero's welcome on Friday.

China and Taiwan have long claimed the islands, which are surrounded by rich fishing grounds and other natural resources. Japan took control of the uninhabited territory, known as Diaoyu in China, in the 1890s after winning the Sino-Japanese war. China's Xinhua news agency reported the first anti-Japanese riots in China since 2010. Protesters reportedly damaged Japanese cars, restaurants and other properties in at least eight cities across the country over the weekend.