Shares of IT companies, which earn a major chunk of their revenue from the US and the Europe, fell sharply on the bourses on Monday on concerns over the US losing its top-notch credit rating due to mounting debts. All the three top IT companies -- TCS, Wipro and Infosys -- witnessed a huge fall in their share prices in morning trade on the BSE.

Shares of the largest IT exporter TCS plunged by 5.18 per cent and were trading at Rs 1,002. Similarly, India's third largest IT company Wipro shed 5.53 per cent and was quoting at Rs 347.65.

The second most weighted scrip on Sensex after RIL, Infosys dropped by 4.51 per cent to Rs 2,473.60. Weakness was seen in the stocks of other IT companies as well, with Tech Mahindra, HCL Tech and Patni Computer losing up to 7 per cent in early trade.

The sharp fall came after the US lost its 'AAA' credit rating for the first time in history, as ratings agency S&P was not convinced with the efforts being made to tackle the country's debt problems.  TCS, Infosys and Wipro rely on the US and European markets for about 60 per cent of their revenue.

Led by losses in these stocks, the BSE IT index was trading down by 4.49 per cent at 5,214 and was the poorest performer among the 13 sectoral indices. This marks a fresh 52-week low for the index. Meanwhile, the BSE benchmark index Sensex lost more than 500 points within minutes of the market opening and was later trading at 16,890.31, down 415.56 points.