China has submitted to the United Nations what it calls geological evidence that would mean disputed islands in the East China Sea close are Chinese territory.

China says its continental shelf extends across to the Okinawa Trough, just off the Japanese island of Okinawa, an area that takes in island territories administered by Japan.

The continental shelf is the relatively gently sloping seabed from the shoreline that ends when the seabed drops off steeply to much greater depths. Waters on the continental shelf are usually around 600 feet at most.

A nation's territorial sea is generally 12 nautical miles offshore. A country's exclusive economic zone -- giving it control over natural resources -- can extend up to 200 nautical miles from the edge of its territorial sea, taking in the continental shelf.

Countries wishing to claim an exclusive economic zone further than 200 nautical miles must apply to the United Nations for a review of geological evidence.

Details of China's claim are in its presentation Partial Submission Concerning the Outer Limits of the Continental Shelf beyond 200 Nautical Miles in the East China Sea.

State-run Xinhua news agency reported Chen Lianzeng, deputy head of China's State Oceanic Administration, saying geological characteristics show that the continental shelf in the sea is the natural extension of China's land territory.

The United Nations is considering a backlog of challenges to maritime demarcations and so it is unlikely a decision will be taken soon, he said.

China will continue to press its claim to the Diaoyu Islands -- known as Senkaku in Japan -- which lie outside China's 200-nautical-mile limit and within Japan's limit.

Taiwan also claims the Diaoyu Islands.

At the end of World War II in 1945 the islands were under U.S. jurisdiction as part of the captured Japanese island of Okinawa. But they have been under Japanese jurisdiction since 1972 when Okinawa was returned to Japan.

Tensions flared between Beijing and Tokyo in September after the Japanese government bought three of the islands from a private Japanese owner, triggering public protests in Chinese cities.

Since then China has stepped up naval incursions and patrols around the islands for which Japan has lodged formal diplomatic complaints.

China also has commissioned its first aircraft carrier, which will begin patrolling the South and East China seas, making uneasy other countries with which China has maritime territorial disputes.

At last month's Association of Southeast Asian Nations meeting in the Cambodian capital Phnom Penh, Japanese Prime Minister Yoshihiko Noda said Japan remains committed to a peaceful solution to territorial disputes in the South China Sea.

"Japan remains committed to dealing with any outstanding issues in a calm and peaceful manner," Noda said.

He stressed that the Japan-China relationship is "one of the most important bilateral relationships for Japan."

A report by the Japanese news agency Kyodo at the time said Noda's remarks reflect Japan's vigilance of China's rapid naval expansion in resource-rich Asian waters, an issue which should be a "common concern for the international community."