Japan registered a protest to China on Thursday over the Chinese Communist Party’s main propaganda organ, the People’s Daily newspaper, questioning Tokyo’s historical claim on Okinawa, Japan's southern-most prefecture, which is also considered a key strategic asset for the U.S. in the Asian region.

In a lengthy article in the People's Daily, two academics from China's top state-run think-tank said: “History’s unresolved questions relating to the Ryukyu [which includes Okinawa] have reached a time for reconsideration,” the Wall Street Journal reported.

Citing treaties from the Sino-Japanese war and from World War II, the article argued that ownership of the Ryukyu islands should be discussed.

One of the authors of the controversial article, Zhang Haipeng, argues that Japan robbed China of Taiwan and its affiliated islands, including the Senkakus, the Pescadores and Okinawa, when the two nations concluded the Treaty of Shimonoseki following the Sino-Japanese War (1894-1895), as reported by Japan’s Asahi Shimbun newspaper.

He wrote that the Senkaku islands were returned to China after World War II ended in 1945, but the issue of sovereignty of Okinawa is yet to be resolved.

Okinawa was a major battlefield during World War II and a U.S.-administered territory until 1972. Some 50,000 U.S. troops are stationed in Japan, of which a significant number is based in Okinawa.

Japan and the U.S. consider maintaining American soldiers in Okinawa bases critical to counter-balance China's rising influence in the region.

On Wednesday, China’s Foreign Ministry spokeswoman Hua Chunying indicated the country may have rights to Okinawa.

“The history of Ryukyu and Okinawa is a problem that the academic society has long been paying close attention to," said Hua when asked about Japan's sovereignty over Okinawa during a news conference, the BBC reported.

In Tokyo, Chief Cabinet Secretary Yoshihide Suga said Japan will not accept China’s claim to rights over Okinawa.

“If the article represents the stance of the Chinese government, we can never accept that,” Suga told a news conference on Thursday.

He also said Japan has voiced its protest against the article to the Chinese government. The official response from Chinese officials, according to Suga, was “the researchers have written the article in their private capacities.”

The controversy over Okinawa has come amid a longstanding dispute over Senkaku, a small group of uninhabited islands known as Diaoyu in China. Tensions have been simmering ever since the Japanese government signed a contract worth 2.05 billion yen ($26 million) in September last year to buy three of the five main islands from their private owner.

The islands, which lie some 200km (124 miles) off Okinawa and beyond China's 200 nautical mile (370km) exclusive economic zone, are surrounded by an area rich in fisheries and are believed to contain significant hydrocarbon resources.

China has laid claim to the islands since the U.N. returned them to Japanese sovereignty in accordance with the Okinawa Reversion Agreement that ended the U.S. occupation of Okinawa.