China-Japan row sparks protests
Protesters shout slogans at the start of anti-China demonstrations in central Tokyo on Saturday.
Tensions are running high between China and Japan since a diplomatic row broke out between the two sides in the wake of a maritime collision in September.
Thousands of Japanese nationalist groups rallied near the Chinese Embassy in Tokyo on Saturday. They claim the islands in the East China Sea are Japanese territory and accuse Beijing of invading them.
The uninhabited region is called Senkaku in Japan and Diaoyu in China and is known have vast natural resources.
"China has expressed its deep concern to Japan over this," Foreign Ministry spokesman Ma Zhaoxu said in a statement on the ministry website, Xinhua reported.
"We urge the Japanese side to ... take effective measures to ensure the safety of China's embassy, consulates, institutions and personnel in Japan."
However, rival demonstrations have also been held in at least three Chinese cities against Japan's claim to the region.
The dispute sparked last month when Japan detained a Chinese captain near the islands, after his vessel collided with two Japanese coastguard ships. He was released last month after being held for 17 days in custody.
JR/HGH/MMN