Tracking weak global markets, the Sensex at the Bombay Stock Exchange fell 103 points, or 0.6 per cent, to 17,602 in opening trade, today, on continued selling by investors, amid fresh concerns about the euro-zone debt crisis.Afterwards the Sensex lost further ground, and stood 181 points, or 1 per cent in negative territory, at 17,524 a short while ago.Other Asian markets in Japan, Hong Kong, Indonesia, and Singapore were down by between 0.9 percent and 1.8 percent, as softer-than-expected Chinese manufacturing data, and fresh worries about the euro-zone debt crisis dulled the appeal of risky assets.