The index saw some upward bias and clocked 27,000-level in the mid-session on reports of monsoon hitting Kerala coast but failed to sustain the gains.
Greece postponing repayment of an IMF loan added to negative sentiment already hit by RBI's cautious stance on economic recovery and forecast of a "deficient" monsoon.
"Global market is cautious regarding Greek issue. Global bond yields are inching up while oil and commodity prices are consolidating. In such environment Indian market is volatile led with disappointment post RBI meet," said Vinod Nair, Head-Fundamental Research of Geojit BNP Paribas Financial.
However, on across-the-board selling towards the fag-end, the Sensex again slipped into negative zone and closed the session 44.93 points or 0.17 per cent down at 26,768.49.
The 50-issue NSE Nifty also fell by 15.95 points or 0.20 per cent to 8,114.70. It shuttled between 8,191.00 and 8,100.15 during the session.
Both the indices, Sensex and Nifty, ended in the negative zone for second straight week.
ICICI Bank fell the most among Sensex stocks by dropping 2.18 per cent, followed by Tata Motors 2.11 per cent.
Meanwhile, Nestle continued its slide and shed 0.23 per cent to Rs 5,997.10 after the company decided to take Maggi off the shelves following a controversy over its contents, prompting several states to ban the 'two-minute' noodles.
Meanwhile, foreign and domestic investors bought shares worth Rs 511.90 crore and Rs 772.04 crore, respectively, yesterday as per provisional data.
