The Bombay Stock Exchange benchmark Sensex opened nearly 129 points higher on Monday on emergence of buying in fundamentally strong shares at lower levels, driven by a firming trend on other Asian bourses.The 30-share barometer, which lost nearly over 480 points in the previous two sessions, rose by 128 points, or 0.72 per cent, to 18,007 in the first few minutes of trade on Monday.In a similar fashion, the wide-based National Stock Exchange Nifty index rose by 39.60 points, or 0.73 per cent, to 5,413.In the Asian region, Hong Kong's Hang Seng index rose by 1.30 per cent in morning trade on Monday, while the US Dow Jones Industrial Average ended 0.71 per cent higher in the previous session on Friday.