The Indian equity benchmarks extended losses for fourth session in a row on Wednesday on the back of a broad-based selling pressure amid rising Covid-19 cases in the country. The benchmarks opened higher but soon edged lower owing to heightened volatility. The Sensex fell as much as 645 points and Nifty 50 index briefly dropped below its important psychological level of 14,700.The Sensex dropped 562 points to close at 49,802 and Nifty 50 index fell 189 points to end at 14,721.The country is dealing with a fresh surge in Covid-19 cases, with daily infections jumping by 28,903 on Wednesday, the highest increase since December 13.Reliance Industries, HDFC Bank, ICICI Bank, Kotak Mahindra Bank, State Bank of India and Axis Bank were among top drags in the Sensex.Selling pressure was broad-based as all the 11 sector gauges compiled by the National Stock Exchange ended higher led by the Nifty PSU Bank index’s nearly 4 per cent fall. Nifty Media, Metal, Auto, Banking, Pharma and Realty indexes also fell between 1-3 per cent.Mid- and small-cap shares underperformed their larger peers as Nifty Midcap 100 and Nifty Smallcap 100 indexes fell over 2 per cent each.On the primary market front, Nazara Technologies shares were in high demand in the ongoing share sale via initial public offering (IPO). The Rakesh Jhunjhunwala-backed gaming company’s Rs 582.91 crore IPO was oversubscribed within hours of opening. The IPO was subscribed 3.28 times till 3:50 pm, data from the National Stock Exchange showed.Selling pressure was so intense that only two shares in the Nifty 50 basket managed to close higher. Bharat Petroleum was top Nifty loser, the stock plunged 5 per cent to Rs 431 after it declared a second interim dividend of Rs 5 per share.ONGC, Tata Motors, Adani Ports, Coal India, GAIL India, Sun Pharma, State Bank of India, SBI Life, NTPC, Cipla, Bajaj Auto, IndusInd Bank, Tata Steel and Hindalco also fell 2.4-4.7 per cent.On the flipside, ITC and Infosys were the notable gainers.The overall market breadth was extremely negative as 2,148 shares ended lower while 837 closed higher on the BSE.