The Sensex at the Bombay Stock Exchange fell 66 points, or 0.4 per cent, to 16,086 in in opening trade, this morning, on continued selling by investors, and in line with a weak trend on the other Asian bourses. Afterwards, selling presure intensified, and the Sensex lost considerably more ground, to stand 331 points, or 2.1 percent in negative territory, and slip below the key 16,000 level, at 15,820, in afternoon deals, a short while ago. The 30-share Sensex has already lost nearly 550 points in the past two trading sessions.Other Asian markets in Japan, Indonesia, Hong Kong, South Korea and Singapore were down by between 0.7 percent and 3.5 percent, today, on growing concerns about Europe's debt troubles. Across in the US, the Dow Jones Industrial Average had plunged 2.4 per cent, overnight.