Sensex and Nifty closed in red for sixth consecutive day on Friday as they hit three-week lows. Sensex closed 733.22 points lower at 80,426.46, and Nifty ended 236.15 points or 0.95% lower at 24,654.70. Barring six companies, all other Nifty 50 constituents traded in the red. Mahindra and Mahindra, Eternal and Tata Steel were the top losers at Sensex.