The Sensex at the Bombay stock Exchange declined 104 points, or 0.6 per cent, to 17,494 in opening trade, today, on profit-booking by funds and retail investors, amid subdued regional bourses. Afterwards, the Sensex continued weak, and stood 127 points, or 0.7 per cent in the negative zone, at 17,471 in afternoon deals, a short while ago. The 30-share Sensex had gained nearly 540 points in the past three trading sessions.Key stock indices in Japan, Indonesia, Singapore and South Korea were down by between 0.6 percent and 2.3 percent, today. The US Dow Jones Industrial Average had slipped 0.5 per cent, overnight, as the prospect of further monetary easing by the Federal Reserve receded.