Mumbai, Aug 5 - A key index of the Indian equities markets slipped after rising almost 143 points soon after the opening bell Wednesday, and was ruling just 11.58 points up, about an hour into trading.

The sensitive index (Sensex) of the Bombay Stock Exchange (BSE) opened higher at 15,882.39 points, as against Tuesday's close at 15,830.98 points. But it slipped to 15,848.32 points, 17.34 points or 0.11 percent down.

The broader S&P CNX Nifty of the National Stock Exchange (NSE), too gave up its morning gains and was ruling in the negative terrain at 4,677.25 points, a fall of 0.07 percent.

Broader market indices were trading on a flat note, with the BSE midcap index around its previous closing figure, and the BSE smallcap index up 0.34 percent.