Mumbai: Plummeting for the third straight session, the BSE benchmark Sensex lost nearly 177 points in opening trade on Thursday in the wake of the latest 50 basis points short-term lending rate hike by the RBI, amid fears of even further monetary tightening to rein in inflation.

The 30-share Bombay Stock Exchange barometer, which lost over 439.04 points in the previous two sessions, fell further by 176.56 points, or 0.95 percent, to 18,255.69 in the first few minutes of trade on Thursday.

The wide-based National Stock Exchange index Nifty index also took a beating in early trade, shedding 55.50 points, or 1 percent, to trade below the 5,500 points level at 5,491.30.

Stocks of banking, realty, auto, oil and gas and IT firms were mainly under pressure, dragging the Sensex down.

Brokers said continued offloading of stocks by funds and retail investors after the RBI raised the short-term lending rate by 50 basis points on Tuesday and fears of further monetary tightening to control inflation mainly dampened the trading sentiment.

In addition, the negative sentiment persisting in global markets on US debt default worries and concerns over the euro zone crisis also had a negative impact, besides monthly expiry in the derivatives segment, they said.

In Asia, Hong Kong's Hang Seng Index was down 1.08 percent, while Japan's Nikkei lost 1.24 percent in early trade on Thursday morning. In the US, the Dow Jones Industrial Average ended 1.59 percent lower in Wednesday's trade.