BSE Sensex firmed up by 261 points in afternoon trade on good buying inquiries mainly in realty, consumer durable, auto, refinery and capital goods sectors. The 30 share index snapped its three-day losing streak by rising 196 points in opening trade today, before quoting at 19081 points a short while ago.In a similar manner, the National Stock Exchange Nifty was up by 78 points, to reach 5,777.