Mumbai: The BSE benchmark Sensex tumbled by over 262 points in opening trade on Monday amid sustained selling pressure influenced by a weakening trend in Asian markets on worries over the euro zone debt crisis.

The 30-share index, which lost 244.31 points in the previous session on Friday, plummeted further by 262.16 points, or 1.59 percent, to 16,191.60 in opening trade on Monday.

In a similar fashion, the wide-based National Stock Exchange Nifty index declined by 77.45 points, or 1.57 percent, to 4,865.80, led by stocks of metal and banking firms.

Brokers said sustained selling by funds amid a weakening trend on other Asian bourses and concerns about the debt crisis in the euro zone mainly dampened the trading sentiment here.

In the Asian region, Hong Kong's Hang Seng Index was down by 3.03 percent, while Japan's Nikkei declined by 2.26 percent in early trade on Monday.