BEIJING - Senior Chinese leader He Guoqiang on Friday reiterated China's firm resolution to safeguard its sovereignty over the Diaoyu Islands.

He, a member of the Standing Committee of the Political Bureau of the Communist Party of China (CPC) Central Committee, made the remarks as he met with visiting Polish Foreign Minister Radoslaw Sikorski.

He's remarks came after the Japanese government on Tuesday signed a contract with a "private owner" to "purchase" the Diaoyu Islands.

Reviewing a painful period of history, He said both China and Poland suffered serious losses during World War II.

Since the end of the war, in accordance with the Cairo Declaration and the Potsdam Proclamation, the Diaoyu Island and its affiliated islands, usurped by Japan, have been returned to China according to international law, He said.

Japan's "purchase" has seriously violated China's territorial sovereignty, He said, adding that the Japanese government's move is a denial of the outcome of World War II and constitutes a grave challenge to post-war international order.

The Diaoyu Island and its affiliated islets have been an inalienable part of China's territory since ancient times and China has indisputable sovereignty over them, He said.

"We will resolutely safeguard our sovereignty over the Diaoyu Islands," He said.

Sikorski expressed understanding of China's feelings regarding its sovereignty, as well as his hope that the dispute will be resolved appropriately through dialogue between the concerned parties.

He and Sikorski also pledged to boost cooperation between both sides and advance their bilateral strategic partnership in a sustainable way.

On Friday, Foreign Minister Yang Jiechi held talks with Sikorski to exchange views on boosting bilateral ties and other issues of common concern.