After the end of the Second World War, the Diaoyu Islands and other islets invaded and occupied by Japan have already been returned to China according to the Cairo Declaration and the Potsdam Proclamation, Yang said.
The unilateral island-buying move by the Japanese government, along with other provocations, have gravely infringed on China's territorial sovereignty, he said.
Japan's position on the issue is also an outright denial of the outcomes of the victory of the World Anti-Fascist War and constitutes a grave challenge to the post-war international order as well as the purposes and principles of the UN charter, he said.
The Chinese government, he said, stands firm to safeguard its territorial sovereignty, urging the Japanese side to stop immediately all the acts which would damage China's territorial sovereignty, to correct its mistakes with real actions and to make genuine efforts to properly handle the current situation.
Yang noted that the ASEM summit is a platform where countries from Asia and Europe seek to conduct mutually-beneficial cooperation and work for common development.
Japan, regardless of the bigger picture of the Asia-Europe cooperation, intentionally provokes the Diaoyu Islands issue at the meeting. Such a move is totally unpopular and doomed to fail, Yang said.
Landmark building should respect the public's feeling