BEIJING - China has moved to bolster its legal position in a volatile territorial dispute with Japan, state newspapers said on Monday, warning that Japan could endure another "lost decade" of economic stagnation if Beijing turns to trade retaliation.

The volley of warnings from Chinese officials and newspapers came after a weekend of protests across dozens of cities, some of them violent. Japanese Prime Minister Yoshihiko Noda urged Beijing to ensure Japan's people and property were protected.

The ruling Chinese Communist Party, which rarely allows street protests, opened the door to the display of public anger after Japan's decision last week to buy disputed East China Sea islands, which Tokyo calls the Senkaku and Beijing calls the Diaoyu, from a private Japanese owner.

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