The BSE benchmark Sensex today was down by over 300 points during noon. The 30-share index which fell sharply by while opening in the morning,continued to be in the red and was down 312 points to trade at 18,230 .Similarly, the wide-based National Stock Exchange index Nifty also declined by 77 points, or 1.38 per cent, to 5,517.In the Asian region, Hong Kong's Hang Seng index was up by 0.15 per cent, while Japan's Nikkei Index shed 0.52 percent in the morning trade today.The US Dow Jones Industrial Average ended 0.42 per cent higher in yesterday's trade.