Four Chinese surveillance ships have entered waters near disputed Japanese-controlled islands in the East China Sea, further intensifying a bitter territorial dispute.

Japan's Foreign Minister Koichiro Gemba said Tuesday authorities have called on the ships to leave the Japanese waters, and that a complaint has been lodged with China's government.

In Beijing, a Chinese foreign ministry spokesman said the four surveillance ships were patrolling waters near the islands, known in Japan as Senkaku and in China as Diaoyu. The spokesman also said China opposes what he called an illegal entrance into the waters by “Japanese right-wingers.” He described the move as a “provocation.”

China and Japan both claim control of the uninhabited islands, which are surrounded by rich fishing grounds and potential energy deposits. China has been sending patrol and surveillance ships and fishing boats into the area.

There are concerns the dispute may hurt the strong economic relationship between China and Japan, Asia's two largest economies.

Last week, Japanese coast guard ships exchanged water cannon fire with coast guard vessels and fishing boats from Taiwan, which also claims the islands.