Markets continued to decline for the third day and dropped below 18,000 level to 17,970.98 in late morning trade due to persistent selling pressure from investors amid sustained unloading by foreign funds.
Sharp depreciation of rupee value against the dollar in early trade weakened the market sentiment as the domestic currency breached 64-mark level.
The sensex resumed lower at 18,142.83 and dropped further to a low of 17,970.98 before quoting at 18,167.27 at 1050hrs, showing a loss of 140.25 points or 0.77 per cent from its last close.
The NSE 50-shares Nifty also declined by 41.15 points or 0.76 per cent to 5,373.60 at 1050hrs.
Foreign institutional investors (FIIs) sold shares worth a net Rs 680.08 crore yesterday as per provisional data from the stock exchanges.
Most Asian stocks retreated in the early trade triggered by a fourth straight day of losses on the Wall Street. Key benchmark indices in Indonesia, Singapore, Hong Kong, Japan, South Korea and Taiwan were down by 0.15 pct to 4.69 pct while China's Shanghai Composite rose 0.08 pct.