The Sensex regained the crucial 16,000-point level in opening trade on the Bombay Stock Exchange today, surging by over 326 points on fresh buying triggered by a firming trend in other Asian markets. The 30-share index, which had lost nearly 650 points over the past three sessions, surged to 16,175 in the first few minutes of trade today.The wide-based National Stock Exchange Nifty also opened higher by 90 points, at around 4,838.