LONDON, April 30 : The Japanese yen surged on Thursday, following stark warnings from Tokyo officials, including the finance minister, that intervention to prop up the currency could be imminent. Dollar/yen was last trading at 156.56, down more than 2 per cent on the day in an eye-popping move that had traders speculating about whether the move reflected intervention. Japanese finance ministry's foreign exchange division could not be reached for immediate comment. TOMMY VON BROMSEN, FX