The Bombay Stock Exchange benchmark Sensex today rose by 104 points in opening trade on sustained buying by foreign funds. The 30-share index gained 104.09 points, at 17,790.33 points, a level not seen since February 2008. The wide-based National Stock Exchange index Nifty regained 5,300 points level after February 28, 2008 to trade 32.95 points higher at 5,310.85 points. Brokers attributed gains in stocks to firming trend on other Asian bourses, which were up by almost 0.50 per cent in the morning trade.