Profit-booking by wary investors due to expiry of futures and options contract on Thursday and fresh capital outflows also affected the market sentiment.
The sentiment further dampened after the rupee slipped past the 63-mark versus dollar.
Almost all sectors witnessed selling pressure, led mainly by interest rates related stocks from Realty, banking and Auto segments. Metal and Power sectors also suffered losses.
The Sensex resumed lower at 20,899.03 and fell further to more than two-month low of 20,343.78 before settling the week at 20,513.85, still showing a loss of 619.71 points or 2.93 per cent. It had gained by 375.07 points or 1.81 per cent in the previous two weeks.
The NSE 50-share Nifty also dropped by 177.25 points or 2.83 per cent to end at 6,089.50. It had also risen by 95.30 points or 1.54 per cent in the previous two weeks.