The BSE benchmark Sensex on Thursday slumped below the 20,000-mark during mid-session by losing a whopping 364 points, on sustained selling triggered by weakness in other Asian bourses.

The 30-share index started the day on a bearish note at 19,971.37 and nosedived by 364.80 points to 19,697.40 at 1230hrs, with all the sectoral indices, led by realty and capital goods trading in negative territory with losses up to 5.92 per cent. It had lost nearly 224 points in the previous three sessions.

Similarly, the broad-based National Stock Exchange index, Nifty, dropped by 100.60 points to 5,993.90, after touching a low of 5,972.40 intra-day.

Federal Reserve Chairman Bernanke signaling on Wednesday that monetary stimulus may be scaled back if the US economy improves further, triggered selling activity in the entire Asian region, traders said.

In a bid to give assurance to the market following Bernanke’s comments, Finance Minister P Chidambaram on Thursday said: “There is no need for any kind of nervousness.”

Also, reports of manufacturing activity in China contracting in May for the first time in seven months dampened the trading sentiment further, traders added.

Major losers were ICICI Bank, Maruti Suzuki, State Bank of India, Reliance Industries, Infosys, Bajaj Auto, Bharti Airtel, BHEL, Larsen and Toubro, Mahindra and Mahindra , Jindal Steel, Ranbaxy Laboratories and Sterite Industries.