A Chinese research vessel was seen to be lowering what appeared to be a wire into the sea within Japan's exclusive economic zone on Wednesday, the government said.

The Foreign Ministry suspects the ship may have been conducting an unauthorized marine survey and said it had lodged a protest with China.

A Japanese coast guard patrol boat detected the "Xiang Yang Hong 18" carrying out a suspicious maneuver around 130 kilometers northeast of Taisho Island, one of the uninhabited islets that make up the Tokyo-controlled, Beijing-claimed Senkaku Islands in the East China Sea, at about 8:10 a.m. on Wednesday, the government said.

The Japanese coast guard urged the vessel over the radio to cease such an action.

The ministry said China had not obtained consent from Japan for a marine survey in the area, adding that if Beijing was indeed performing scientific research, it would be "extremely regrettable."

China's military activities and maritime assertiveness have become more intense in the East and South China seas and Tokyo has protested repeated intrusions by Chinese vessels into Japanese waters near the Senkakus.

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