The Bombay Stock Exchange benchmark Sensex on Wednesday opened higher by almost 120 points at18,091. The gain in the sensex is due to emergence of fund buying in auto, oil,gas, realty and metal stocks, coupled with a firming trend in the other Asian markets. The sensex was trading at 18104, up by 133 points when reports last came in. Similarly nifty of National Stock Exchange gained 35 points at 5437. The Japanese Nikkei gained 0.10 per cent, while the HongKong's Hang Seng up by 0.15 per cent in the morning trade today. The US Dow Jones Industrial average ended 0.05 per cent higher on Tuesday.