Tracking losses from global markets, domestic benchmark indices Sensex and Nifty opened in the red zone on Friday. However, the indices later erased the losses of the morning's trading session as Sensex gained by 242.52 points or 0.72 per cent to close at 33,780.89 while Nifty increased by 70.90 points or 0.72 per cent to settle at 9,972.90.