China's top newspaper on Wednesday published a call for a review of Japan's sovereignty over the island of Okinawa -- home to major US bases -- with the Asian powers already embroiled in a territorial row.
The lengthy article in the People's Daily, China's most-circulated newspaper and the mouthpiece of the ruling Communist party, argued that the country may have rights to the Ryukyu chain, which includes Okinawa.
The island is home to major US air force and marine bases as well as 1.3 million people, who are considered more closely related to Japan in ethnic and linguistic terms than to China.
The authors of the article, two scholars at the Chinese Academy of Social Sciences, considered China's top state-run think-tank, said the Ryukyus were a "vassal state" of China before Japan annexed the islands in the late 1800s.
"Unresolved problems relating to the Ryukyu Islands have reached the time for reconsideration," wrote Zhang Haipeng and Li Guoqiang, citing post-World War II declarations that required Japan to return Chinese territory.
The article also repeated Chinese government arguments for China's historical claims over a set of tiny uninhabited islets in the East China Sea known as Diaoyu in Chinese and Senkaku in Japanese.
The two nations have stepped up a war of words over the dispute in recent months, with Beijing's vessels regularly entering the waters around the Tokyo-controlled islands, stoking fears of armed conflict.
Questions over Japan's right to Okinawa were probably aimed at raising the stakes in the East China Sea dispute, said Willy Lam, an expert on Chinese politics at the Chinese University of Hong Kong.
"I think this is psychological warfare," he said, adding: "The major point is to put pressure on Japan so that the Japanese administration will be forced to make concessions over the Senkaku islands."
Okinawa is the biggest of the Ryukyu islands, which stretch for about 1,000 kilometres (600 miles) from Japan's mainland, and were the centre of the Ryukyuan kingdom that paid tribute to Chinese emperors until it was absorbed by Japan in 1879.
But some Chinese see historical ties as a basis for sovereignty and dismiss Japan's possession of the islands as a legacy of its aggressive expansionism that ended in defeat at the end of World War II.
China's government does not make such claims, but state media have from time to time carried articles and commentaries questioning Japan's authority.
China is also in dispute with southeast Asian neighbours over huge swathes of the South China Sea, which it claims based on a map published in the 1940s.
Analysts have said that Beijing is growing increasingly assertive in pressing its territorial claims, while nations across Asia have invested massively in upgrading their naval capacity.
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