Tokyo's Nikkei average plunged more than four percent by late Monday afternoon, falling below 11,000 for the first time since February as the prospect of higher U.S. interest rates stoked fears of further Wall Street losses. Selling was fueled also after the United States embassy in Japan issued an e-mail warning to U.S. citizens on Monday about a possible bomb attack against the mission this week, though adding it was unable to determine whether the threat was credible. The Nikkei <.N225> fell 4.21 percent, or 482.09 points, to 10,956.73 by 0527 GMT, sinking below the closely watched 11,000 line for the first time since February 27 on an intraday basis. The broader TOPIX index <.TOPX> fell 5.20 percent to 1,091.08.|||