The Sensex registered its sharpest decline in four weeks today, plummeting by nearly 198 points as investors offloaded interest rate-sensitive stocks amid fears of an impending rate hike by the RBI. The 30-share Sensex index of the Bombay Stock Exchange, which lost over 62 points in yesterday's session, closed 198 points lower at 20,301 today. In a similar fashion, the broad-based National StockExchange Nifty index fell by 66 points to 6,080. The decline was led by banking, realty, auto and capital goods stocks over fears the Reserve Bank of India might raise interest rates to curb rising inflation, which could have the unwanted effect of slowing down economic growth and investment.