The government has lodged "a strong protest" against a commentary published by a Chinese state-run newspaper that questioned the legitimacy of Japan's ownership of Okinawa, Chief Cabinet Secretary Yoshihide Suga said Thursday.

"If that is the position of the Chinese government, it's totally unacceptable for us," the government's top spokesman told a news conference.

According to Suga, Beijing said the article was penned by the authors in their capacity as private persons. He declined to elaborate further on China's reaction.

The Wednesday edition of the People's Daily carried the commentary by Zhang Haipeng and Li Guoqiang, who are employed as researchers at the Chinese Academy of Social Science.

They argued that China can already claim Taiwan and the Senkaku Islands because Japan, when it surrendered in World War II, accepted agreements over territorial ownership made by the Allies.

Ownership of the Ryukyu Islands, which encompass Okinawa, can be questioned under the same basis, they wrote.

The argument was seen as an attempt by China to raise the ante in the territorial dispute over the Senkakus, which sit roughly 150 km north of Okinawa Prefecture's Ishigaki Island and 150 km east of Taiwan. China claims the isles as Diaoyu and Taiwan as Tiaoyutai.

Bilateral tensions climbed after Japan nationalized three of the five islets in September, touching off riots throughout China and diplomatic repercussions with Beijing.