Anti-Japan protests reignited across China on Tuesday, the sensitive anniversary marking Tokyo's occupation of its giant neighbour, escalating a maritime dispute which has forced major Japanese firms to suspend business there.

China reacted swiftly to the news of the landing, which risked inflaming a crisis that already ranks as China's worst outbreak of anti-Japan sentiment in decades. Beijing described the landing as provocative, lodged a complaint with Tokyo and said it reserved the right to take further action.

Japan's coastguard said three Chinese maritime surveillance ships briefly entered what Japan considers its territorial waters around the disputed islets on Tuesday, further raising tensions, although they and seven other nearby ships had left the area by late evening. It was the second such incident since Friday, when six ships briefly entered the waters.

The dispute over the uninhabited group of islands in the East China Sea - known as the Senkaku in Japan and Diaoyu in China - led to another day of protests in China that were accompanied by heavy security. Relations between Asia's two biggest economies have faltered badly, with emotions running high on the streets and also out at sea where two Japanese activists landed on an island at the centre of the dispute.

Japanese businesses shut hundreds of stores and factories across China and Japan's embassy in Beijing again came under siege by protesters throwing water bottles, waving Chinese flags and chanting anti-Japan slogans evoking war-time enmity.

Japanese Prime Minister Yoshihiko Noda urged Beijing again to protect Japanese citizens in China.