The Sensex at the Bombay Stock Exchange remained weak in afternoon trade, and stood 109 points, or 0.5 percent in negative territory, at 20,780 a short while ago. Earlier in the morning, the Sensex had declined 110 points, or 0.5 percent, to 20,779, on sustained selling by funds and retail investors, amid falling regional markets. The Sensex had lost over 280 points in the previous two trading sessions.Stock indices in China, Hong Kong, Taiwan, Singapore, Indonesia, and South Korea had lost between 0.7 percent and 1.9 percent, today. The US Dow Jones Industrial Average ended 0.8 per cent lower in yesterday's trade