China says it has filed a formal protest with Japan over Tokyo's plans to name uninhabited Pacific islands claimed by both countries.

In a statement Monday, a Chinese Foreign Ministry spokesman (Liu Weiman) insisted China has “indisputable sovereignty” over the East China Sea islands, known as Diaoyu in China and Senkaku in Japan.

The Japanese plan, announced earlier this month, would name 39 islets — some of them a part of the dispute over competing claims to a large natural gas field and fishing rights.

Japan claims the area as part of its exclusive economic zone, while Beijing claims the islets have been “an inherent part of China” since ancient times.

In 2010, relations between Asia's two largest economies sank to the lowest point in years, after Japan arrested the captain of a Chinese fishing boat that collided with a Japanese military vessel patrolling near the disputed chain.

A year later, Japan deployed a new Coast Guard to protect its claim to the island chain. But Beijing and Tokyo later agreed to work toward developing a crisis management mechanism to head off future maritime disputes.