The BSE Sensex today tanked over 221 points in early trade on fresh selling after three sessions of gains. The 30-share index lost over 221 points, or 1.19 per cent, to trade at around 18,337 with banking, realty, metal PSUs and oil and gas sector stocks leading the fall. Sensex had gained over 652 points in the previous three sessions.Similarly, the wide-based National Stock Exchange Nifty declined by nearly 81 points, or 1.48 per cent, to around 5,395.