Angry anti-Japan activists called on the central government to take a tougher line after the Japanese government gave a company permission to conduct exploratory drilling in a gas field in disputed waters in the East China Sea. Tong Zeng , chairman of the China Federation for Defending the Diaoyu Islands, said the move showed Japan was trying to impose its 'median line' - the boundary of its self-declared exclusive economic zone - on China and the international society. 'They want to tell the world that Japan has a sovereign right to that area, but their unilateral action has actually violated international laws,' Mr Tong said. He said Japan was causing trouble now because it knew China was aiming for good relations with its neighbours so that it could concentrate on economic development. 'Japan is a sly country and it knows China is soft at this time,' he said. 'What they have is [government] action, but what we have is only verbal protest, which is always a weak voice in the international press.' The high-profile activist urged the central government to take a tough diplomatic and military stance on the issue. 'China should be ready to make any sacrifice to defend its sovereignty and international law, otherwise Japan will reach for a yard after getting an inch,' he said. 'This is also crucial in restraining Japan's further expansion in Northeast Asia.' Mr Tong's stance was shared by Hong Kong activist Or Wah, chairman of the Action Committee for Defending the Diaoyu Islands. 'What Japan has done will only add to the smell of gunpowder in the currently tense bilateral relations,' he said. Mr Or said it seemed that the Japanese authorities had made up their minds to ignore China's request for negotiation. 'I hope the Chinese government can take a stronger stance on this sensitive issue. For instance, we can show our military power over the East China Sea instead of simply making verbal protests,' Mr Or said.