Bombay Stock Exchange benchmark Sensex was trading 128 points down at 18,268 a short while ago. Earlier it plummeted by over 300 points in opening trade on Monday. This follows panicky fund managers and retail investors giving into selling pressure for the fourth consecutive session, prompted by weak global cues amid concerns over the unrest in Egypt. Similarly, National Stock Exchange Nifty was trading 35 points down at 5,476.