New Delhi,   India's key equity indices -- Sensex and Nifty -- extended their losses from the previous week to trade lower in early trade on Monday.

At 9.54 a.m., Sensex was 0.6 per cent or 318 points down at 57,044 points, whereas Nifty was 0.5 per cent or 92 points down at 17,061 points.

Among the stocks, UPL, HDFC, HDFC Bank, Dr Reddy's, and Kotak Mahindra Bank were the top five losers among the Nifty 50 companies, while Bajaj Auto, Cipla, Bharti Airtel, ONGC, and Hindalco were the top five gainers, NSE data showed.

Retail investors have to be more vigilant in their investment by avoiding low-grade stocks and investing in high quality stocks, said V.K. Vijayakumar, Chief Investment Strategist at Geojit Financial Services.