Mumbai, Sep 27 (IANS): Key Indian equity indices provisionally closed deep in the red on Wednesday as caution ahead of futures and options (F&O) expiry, coupled with a weak rupee and profit booking in banking, capital goods and automobile stocks, hampered investors' risk-taking appetite.

According to market observers, sentiment was hampered on updates that the Indian Army inflicted "heavy casualties" on NSCN (K) militants during a firefight along the border with Myanmar.

"Market close on Wednesday would mark the longest losing streak for the indices after a seven-day fall that ended on 22 December, 2016," Dhruv Desai, Director and Chief Operating Officer of Tradebulls, told IANS.

"Sentiment was also dampened, when news agency flashed, there was a firefight and heavy casualties were suffered by the NSCN-Khaplang in Nagaland along the India-Myanmar border, tweeted the Eastern Command," Desai added.

The BSE Sensex shed over 400 points during intra-day trade.

At 3.30 p.m., the 30-scrip Sensitive Index of the BSE provisionally closed at 31,159.81 points -- down 439.95 points, or 1.39 per cent. Intra-day, it touched a high of 31,797.46 points and a low of 31,100.80 points.

The wider 51-scrip Nifty of the National Stock Exchange (NSE) closed below the psychologically important 9,800-level.

It fell by 132.25 points, or 1.34 per cent, to close at 9,739.25 points.

On Tuesday, the benchmark indices closed marginally in the red on the back of continuous outflow of foreign funds and selling pressure in telecom, Teck (technology, media and entertainment) and FMCG stocks.

The Nifty closed at 9,871.50 points -- down 1.10 points or 0.01 per cent, while the Sensex closed at 31,599.76 points -- down 26.87 points, or 0.08 per cent.