The Sensex at the Bombay Stock Exchange fell 83 points, or 0.5 per cent, to 17,036 within the first few minutes of trade, this morning, on continued selling by investors, as weak regional markets dampened sentiment. After a brief recovery, the Sensex again lost ground, to stand 20 points, or 0.1 percent in the negative zone, at 17,098, in afternoon deals, a short while ago. The 30-share Sensex has already lost more than 450 points in the past three trading sessions.Other Asian markets in Japan, Hong Kong, China, Indonesia, South Korea, Singapore, and Taiwan were down by between 0.2 percent and 1 percent, today, after a rise in euro zone bond yields raised fresh doubts about the ability of Italy and Greece to push through painful economic reforms to resolve their debt crises. Over in the US, the Dow Jones Industrial Average had lost 0.6 per cent, overnight.