The Sensex at the Bombay Stock Exchange plunged 348 points, or 1.8 percent, to close at a new three-week low of 19,380, today, as global markets fell, amid concern that the US government could be heading for a shutdown. The Nifty at the National Stock Exchange lost 98 points, or 1.7 percent, to 5,735. Stock markets in Japan, Hong Kong, South Korea and Singapore declined between 0.7 percent and 2.1 percent.