The Sensex at the Bombay stock Exchange fell 153 points, or 0.9 per cent, to 17,081 in opening trade, on Monday morning, as investors booked profits after a six-day winning streak, amid a weak Asian trend. Later, selling pressure intensified, and the Sensex dropped 275 points, or 1.6 percent, to slip below the 17,000 mark, at 16,959 in afternoon deals, a short while ago. The 30-share Sensex had gained over 780 points in the past six trading sessions.Other Asian markets in Japan, China, Hong Kong, Indonesia, South Korea and Singapore were down between 0.3 percent and 1.8 percent, ahead of a meeting of European leaders to discuss the euro-zone sovereign-debt crisis.