Two scholars from an official Chinese research center suggested re-examining the ownership of the Japanese island chain that includes Okinawa, adding to tensions over the Senkaku territorial dispute.

Agreements reached between the Allies during World War II mean the ownership of the Ryukyu Islands may be in question, the Chinese Academy of Social Sciences researchers said in a commentary published Wednesday in the People’s Daily, the Communist Party’s main newspaper. They said Japan’s loss in the war nullified an 1895 treaty in which China ceded territory to Japan.

“It may be time to revisit the unresolved historical issue of the Ryukyu Islands,” Zhang Haipeng and Li Guoqiang wrote in the commentary.

A move to reconsider ownership of the Ryukyus would add to strains as China and Japan each assert their claims over the uninhabited Senkaku Islands in the East China Sea. The central government’s decision last year to purchase three of the islets sparked protests across China.

Tensions were compounded last month when Diet members, including Cabinet ministers, visited Yasukuni Shrine, which is viewed as a symbol of wartime aggression, and Prime Minister Shinzo Abe vowed to protect the Senkaku Islands by force.

“The fact that this view is carried by the People’s Daily signals that Beijing may be upping the ante,” Willy Wo-Lap Lam, an adjunct professor of history at the Chinese University of Hong Kong, wrote in an email. “This is psychological warfare and a classic Chinese negotiation tactic — trying to intimidate the opponent by raising the stakes.”

Okinawa, the largest island in the Ryukyu chain, hosts several U.S. military installations. The scholars’ comments came in an article about China’s claim to the Senkaku Islands.

The Ryukyus unquestionably belong to Japan, Chief Cabinet Secretary Yoshihide Suga said Wednesday. The archipelago has a population of about 1.5 million people and its northernmost point sits 30 km from Kyushu.

“It is clear that in terms of history and internationally, it is our nation’s territory,” Suga said at a briefing. “It’s indisputable. If that is being discussed in China, there is absolutely no basis for it.”

China’s imports from Japan plunged 14 percent in the month following the September protests over the Senkaku Islands, according to Chinese customs figures.

The scholars aren’t necessarily saying that the Ryukyus belong to China, said Taylor Fravel, a professor at the Massachusetts Institute of Technology who studies China’s territorial claims. They are raising the possibility that Japan’s ownership could be disputed because the islands’ rulers in past centuries had tributary relations with imperial China, he said.

“These are perhaps the most serious scholars to date to make this insinuation,” Fravel said.

KEYWORDS China, Okinawa