Taiwan's president has warned Japan over territorial claims made by his Japanese counterpart on a set of Islands in the East China Sea.
The ownership of the Senkaku islands, known as Diaoyu in Chinese, is also subject to claims from Beijing.
Taiwan’s president Ma Ying-jeou responding to recent reports by warning Japan not to “nationalise” the islands and "to resolve the issue in a peaceful way".
Last month, ten Japanese nationalists, who planted flags on the remote island, caused a wave of furious protest across China.
The islands are technically Japanese - the territory was transferred to Japan in 1971 - but China disputes this, claiming the islands have been Chinese for many centuries previous.
An anti-Japan protester holds a poster which reads "Declare War on Japan" in Hangzhou
Last month, members of Gambare Nippon, a group of Japanese nationalists, swam ashore from a protest flotilla to plant the red and white rising sun flag on one of the islands.
They were responding to 14 protesters from Hong Kong, who were arrested after trying to plant a Chinese flag on the same island earlier this week.
The Chinese protesters will be deported, but will not be prosecuted in Japan, Tokyo promised.
Tokyo politician Eiji Kosaka told the AFP: "This is undoubtedly Japanese territory. On the mountain we found Japanese-style houses that had places for drying fish.
"It is very sad that the Japanese government is doing nothing with these islands."
Armed police were called in across China to quell angry anti-Japanese demonstrations.
Crowds of up to 3000 gathered in Shenzhen, Hangzhou, Hong Kong, Guangzhou, Shenyang, Harbin, Qingdao and Chengdu, with Japanese flags set alight. Chinese media said Japanese restaurants and cars were targeted.
Japan has apparently sought to buy more islands in the disputed chain, which currently belong to a private individual - a move China believes is unlawful.
Japanese media reported that the country's ambassador to China is in the process of being replaced, after he criticised the proposal to purchase the islands.
The islands look unimpressive at first glance, but China, Taiwan and Japan all want control of the territory for defensive purposes, and for the rich mineral and oil deposits beneath them.