The markets slipped 2% in late trades as investors turned cautious and booked profits ahead of Ben Bernanke's speech later in the
day, heavy selling in realty and metal shares also weighed.
The Nifty touched a high of 4,861 in the morning session, but gave up all the gains and closed at 4,747, down 92 points, and the Sensex plunged below 16K to end at 15,848, down 298 points.