Japan's trade minister was quoted as saying on Sunday he had information that China had granted companies the rights to conduct natural gas exploration in Tokyo's exclusive economic zone in the East China Sea. It was not clear if Trade Minister Minister Shoichi Nakagawa was referring to the rights being granted in an area near a group of disputed islands known as the Senkakus in Japan and the Diaoyu islands in China. "We have obtained information that construction zones have been designated in several locations within Japan's exclusive economic zone," he said on a Fuji TV programme. Nakagawa suggested that China's suspected move could trigger a diplomatic row, saying: "Ignoring the exclusive economic zone is unfriendly." China earlier this year built a natural gas production plant five km (three miles) from an area that Japan considers to be its exclusive economic zone. Japan is concerned the Chinese project might draw gas from its zone. Japan has repeatedly expressed concern about the project being developed by China near the disputed islands. Following Beijing's move, Tokyo began a geological survey of the disputed area in July, a decision criticized by Chinese state media as dangerous and provocative. Nakagawa said Japan would ask China to clarify whether it has given the green light to the gas project in the area when the two Asian neighbours hold working-level talks later this month.