The BSE benchmark Sensex on Thursday regained the psychological 16,000-point level and closed higher by 274 points, its biggest single-session gain since March 30. The 30-share barometer, after losing 235 points in the past two trading sessions, bounced back to regain 16,000-point level to close at 16,222.30, showing a rise of 274.20 points or 1.72 per cent. Meanwhile, rupee strengthened by 18 paise to trade at 55.82 against the American currency on the Interbank Foreign Exchange market in pre-close trade on Thursday amid selling of the dollar by banks and exporters.