The Sensex on Monday opened nearly 100 points lower. This follows selling by funds and retail investors amid weak Asian markets. The 30-share index, which had gained 46 points in the previous session, shed 99.42 points to 17,856 points. IT, realty, banking, metal and oil and gas stocks came under selling pressure posting losses up to 1.14 per cent. The wide-based National Stock Exchange index Nifty fell by 32.40 to 5,361.50 points. Hong Kong's Hang Seng index shed 0.79 per cent in morning trade, while Japan's financial markets remained closed for a public holiday. The US Dow Jones Industrial Averaged ended 2.52 per cent down on Friday.