Mumbai, Aug 18 (IANS): Key Indian equity indices tumbled during the mid-afternoon trade session on Friday as it became known that Vishal Sikka had quit as the Chief Executive Officer (CEO) and Managing Director (MD) of IT major Infosys.

Heavy selling in IT, healthcare and banking stocks, coupled with negative global cues, hampered investors' risk-taking appetite.

At 1 p.m., the Nifty50 of the National Stock Exchange (NSE) fell by 90 points, or 0.91 per cent, to trade at 9,814.15 points.

The 30-scrip Sensitive Index (Sensex) of the BSE, which opened at 31,729.88 points, traded at 31,451.98 points -- down 343.48 points, or 1.08 per cent, from its previous close at 31,795.46 points.

The Sensex has so far touched a high of 31,729.88 points and a low of 31,429.46 points.

"The benchmark indices opened lower with Nifty50 trading below the 9,850 mark as index heavyweight Infosys cracked after Vishal Sikka resigned as MD and CEO," Dhruv Desai, Director and Chief Operating Officer of Tradebulls, told IANS.

The IT major's scrip on the BSE dipped by 9.77 per cent to trade at Rs 921.40 per share.

The plunge in the stocks of the company led the overall S&P BSE IT index to decline by 354.49 points or 3.39 per cent.

"Nifty PSU Banks, Nifty Pharma were also trading lower in the morning trade, down 1.2 per cent and 0.9 per cent respectively. Top gainers on NSE were Infratel, Indian Oil Corp and Tata Consultancy Services, while on the losing front were Infosys, Zee and Sun Pharma," Desai said.

On Thursday, the benchmark indices closed on a flat note though continuing their streak of gains for the third consecutive session on the back of healthy buying in IT, Teck (technology, media and entertainment) and metal stocks.

The Nifty50 closed at 9,904.15 points -- fractionally up by 6.85 points, or 0.07 per cent, from its previous close.

The Sensex edged up by 24.57 points, or 0.08 per cent, to close at 31,834.45 points.