The Bombay Stock Exchange benchmark Sensex slumped by about 39 points in opening trade today. The extension of the losses for the second straight session is due to sustained selling pressure amid weak global cues.The 30-share index, which had lost 149 points in the previous session, fell further to 19,917 points in the first five minutes of trading.The wide-based National Stock Exchange index Nifty also declined by 6.05 points to 5,985.25 points.Asian markets are trading lower in the early part of the session today after overnight losses in US markets battered the investment sentiment.Hong Kong's Hang Seng Index was down 0.09 per cent, while Japan's Nikkei index fell by 0.41 per cent in morning trade. The US Dow Jones industrial average ended 0.21 per cent down in yesterday's trade.