New Delhi, Feb 28 : India's key indices -- S&P BSE Sensex and NSE Nifty50 -- fell sharply in early trade on Monday as investors are worried about the full-fledged Russia-Ukraine war that is panning out. At 9.55 a.m., Sensex was 1.5 per cent or 817 points down at 55,041 points, whereas Nifty 1.4 per cent or 233 points was down at 16,425 points. "Asian markets are trading mixed in the early Monday trade with Nikkei and HangSeng trading in negative territory while Taiwan and Korean markets trading in positive territory. WTI Crude rose more than 5 per cent on the Russia-Ukraine crisis as Western nations imposed fresh sanctions on Moscow," said Mohit Nigam, Head - PMS at Hem Securities. Nigam believes investors should trade with caution in the next few trading sessions as the volatility is expected to persist for some time. "One can use these dips to open and make fresh positions in quality stocks for the long term." Among the stocks, HDFC Life, SBI Life, Eicher Motors, Maruti Suzuki, and Asian Paints were the top five losers among the Nifty 50 companies, declining 3.1 per cent, 3.1 per cent, 2.7 per cent, 2.6 per cent, and 2.6 per cent, respectively.On the other hand, Power Grid Corporation of India, BPCL, Coal India, Hindalco, and Tata Steel were the top gainers in the opening session, NSE data showed. /IANS