Japan has lodged another protest with China over its continued deployment of a drilling ship at a gas field in a contested area of the East China Sea.

Axar.az reports citing South China Morning Post.

The protest, made through diplomatic channels, followed confirmation by Tokyo that the drilling ship had moved in January to a location a few kilometres northeast of where it was in mid-November, in an apparent search for resources.

“It’s extremely regrettable that China has continued its unilateral development activity,” Chief Cabinet Secretary Yoshihide Suga said on Thursday.

Beijing has developed 16 structures on the Chinese side of a Tokyo-proposed median line separating the two countries’ economic zones in the East China Sea.

Japan and China agreed on joint gas development in the area in 2008 but negotiations were suspended in 2010.

Japan fears China’s unilateral development in the area might lead to the siphoning off of resources from beneath the Japanese side of the line.

The revelation came despite a recent improvement in China-Japan relations.

In the East China Sea, Tokyo and Beijing have been at loggerheads over the ownership of the Senkaku Islands, known as Diaoyu in China, which are administered by Japan but also claimed by China.

The ship in question was found engaged in apparent drilling in September. It then moved in mid-November before its most recent change of location.

The protest followed an agreement by China and Japan on Saturday to accelerate preparations for Chinese President Xi Jinping’s visit to Japan later this year, as the two nations have pledged to promote reciprocal visits by their leaders.

At their meeting in Beijing, Japanese senior deputy minister for foreign affairs Takeo Mori and Chinese Foreign Minister Wang Yi confirmed Xi’s visit to Japan would be “the most important schedule” this year for the two countries.

Wang said China and Japan had to enhance mutual trust and avoid miscalculations to put forward the development of their bilateral relations.