The Sensex at the Bombay Stock Exchange plunged 273 points, or 1.4 percent, to 19,849, in the afternoon trade, a short while ago.The Nifty at the National Stock Exchange dropeed 79 points, or 1.3 percent, to 6,028. In other Asian markets, key indices in Japan, China, Hong Kong, South Korea and Singapore were trading mixed, even as the dollar rose to its four and a half year high against the Yen.