Mumbai, Aug 31 (IANS): Key Indian equity indices -- the NSE Nifty50 and the BSE Sensex - traded on a flat-to-positive note during the mid-afternoon session on Thursday as investors remained cautious on the day of derivatives expiry.

According to market observers, a weak rupee and broadly negative global cues, too, capped gains.

However, healthy buying witnessed in consumer durables and oil and gas stocks kept the sentiments afloat.

Around 12.45 p.m., the wider 51-scrip Nifty of the National Stock Exchange (NSE) traded at 9,893.90 points -- up 9.50 points or 0.10 per cent.

The 30-scrip Sensitive Index (Sensex) of the BSE, which opened at 31,685.44 points, traded at 31,659.36 points -- up 12.90 points or 0.04 per cent from its previous close at 31,646.46 points.

The Sensex has so far touched a high of 31,722.41 points and a low of 31,551.85 points during the intra-day trade.

The BSE market breadth was bullish with 1,170 advances and 765 declines.

"The BSE Sensex opened lower on Monday against the previous session's closing. The broader NSE's Nifty, too, fell in the morning hours. The Indian rupee opened weaker against the US dollar," said Dhruv Desai, Director and Chief Operating Officer of Tradebulls.

"Shares of Wipro and Reliance rose, whereas the shares of NTPC and Sun Pharma fell. Reliance Industries gained 1 per cent after the company said it will make an offer for issuing non convertible debentures (NCDs) worth Rs 2,500 crore next week."

On Wednesday, the benchmark indices surged on the back of positive global cues and healthy buying in metal, oil and gas, and banking stocks.

The Nifty50 closed at 9,884.40 points -- up 88.35 points or 0.90 per cent, while the Sensex closed at 31,646.46 points -- up 258.07 points or 0.82 per cent.