Tension mounted between Taiwan and Japan yesterday over activists' plans to make a helicopter trip on Friday to the Diaoyu Islands. A Taiwan defence spokesman warned Japanese forces not to enter Taiwan's airspace in pursuit of protesters. General Fu Wei-ku said efforts to rescue demonstrators would not be prevented, but warned 'the National Armed Forces will observe, warn and expel . . . any unidentified aircraft entering the Republic of China's air-defence identification zone'. Meanwhile, opposition lawmakers have called for the resignation of the acting director of Taiwan's Civil Aeronautics Administration after he said on Monday that Japanese consent would be needed for the voyage. Addressing the legislature, New Party lawmaker Fu Kuen-chen said that General Chang Kuo-cheng's remarks were 'an insult to the nation' and they had weakened Taipei's claims to the disputed islands.