India's key equity indices plummeted in afternoon session on Thursday after a feeble recovery early on, as concerns about global growth and expectations of ever-tighter interest rates in the United States roiled markets across the world.The S&P BSE Sensex was down nearly 800 points and the NSE'S Nifty50 was below the key 10,300-mark amid market volatility."The sell-off was in sync with the slide in Asian markets after a sharp fall in the US equities on Wednesday. Rising US interest rates, and US-China trade tension will likely hurt corporate profits." Vinod Nair, Head of Research, Geojit Financial Services told IANS.Also, International Monetary Fund head Christine Lagarde's comments that stock market valuations had been "extremely high", triggered the meltdown in the US markets, and spilled over to Asia on Thursday.At one point, the Sensex had crashed 1,000 points, before recouping some of the losses on value buying.Heavy selling was witnessed in banking, IT, metals, auto and capital goods stocks. All 19 sector-based indices on the BSE, except the energy index, traded in the red.At 2.15 p.m., NSE's Nifty traded at 10,240.30, down 219.80 points or 2.10 per cent from its Wednesday's close.The S&P BSE Sensex, which had opened at 34,063.82, traded at 33,967.32, down 793.57 points or 2.28 per cent.So far on Thursday, the Sensex has touched a high of 34,325.18 and a low of 33,723.53.At around 2.00 p.m., the Indian rupee was trading at 74.17 per US dollar, after slumping to a new low of 74.48. The rupee had opened at 74.31 at the Inter-Bank Foreign Exchange Market.