The Sensex at the Bombay Stock Exchange fell 109 points, or 0.5 per cent, to 18,159, in opening trade this morning, on sustained selling by investors, amid weak Asian markets. Later, the Sensex rebounded modestly into positive territory, only to again fall 9 points into the negative zone, at 18,260, in afternoon deals, in volatile trade, a short while ago. The 30-share Sensex has lost more than 220 points in the last three sessions. Other Asian markets in Japan, China, Singapore, Taiwan, Hong Kong and Indonesia were down by between 0.1 percent and 1.2 percent, today.