A local council in southern Japan voted Monday to rename an area including islands disputed with China and Taiwan, a move Beijing denounced as illegal and a "serious provocation".
The local assembly of Ishigaki city approved a plan to change the name of the area covering the Tokyo-controlled Senkaku Islands -- known by Taiwan and China as the Diaoyus -- from "Tonoshiro" to "Tonoshiro Senkaku".
Local media said another part of Ishigaki is also known as Tonoshiro, and the name change was cast as a bid to avoid confusion.
But the uninhabited islands are at the centre of a festering row between Tokyo and Beijing and the move by the small local council -- which does not carry national governmental weight -- sparked anger in both Taiwan and mainland China.
"The passing of the so-called administration designation bill by Japan is a serious provocation to China's territorial sovereignty," Chinese foreign ministry spokesman Zhao Lijian said in response to a question on the issue.
"It is illegal and invalid, and cannot change the fact that the Diaoyu islands belong to China," Zhao added, saying Beijing had lodged "solemn representations to Japan through diplomatic channels and reserves the right to make further responses".
Taiwan says the islands are part of its territory, and also protested the move.
"The sovereignty of Diaoyu islands belongs to our country and any move attempting to alter this fact is invalid," the foreign ministry said in a statement.
It said it had expressed "regret and stern protest" to Tokyo.
Japan's chief government spokesman declined to comment on the Ishigaki council move, but Tokyo has long complained about China's routine dispatch of its coast guard ships to waters surrounding the islands.
Relations between Japan and China deteriorated in 2012 when Tokyo "nationalised" some of the disputed islets and tensions have flared up periodically over the region.
The uninhabited islands are at the centre of a festering row between Tokyo and Beijing