(MENAFN) Japan has formally objected to China’s recent construction activities in a contested section of the East China Sea, escalating tensions between the two nations.

The Japanese Foreign Ministry announced late Monday that China has started erecting a new structure on the Chinese side of the median line dividing their maritime territories.

"It is extremely regrettable that China is advancing unilateral development in the East China Sea while the Exclusive Economic Zone and the continental shelf in the East China Sea have not yet been delimited," the ministry stated.

In response, Kanai Masaaki, Director-General of the Asian and Oceanian Affairs Bureau, lodged a firm protest with Shi Yong, Deputy Chief of Mission at the Chinese Embassy in Tokyo. Kanai pressed China to stop the construction and revive stalled negotiations on resource-sharing.

Japan maintains that the median line, drawn between the two coastlines, represents the official maritime boundary under its domestic law. China, however, claims its exclusive economic zone stretches well beyond this demarcation.

Despite a 2008 agreement to jointly develop gas fields in the area, talks between the two sides have been at a standstill for some time.

China has yet to respond to Japan’s latest protest.

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