Mumbai, July 22 : The key Indian equity indices surged on Thursday morning with the BSE Sensex gaining over 500 points. The Nifty50 on National Stock Exchange (NSE) was also trading above the 15,750-mark. The across-the-board rise was led by metal and finance stocks. Around 10.30 a.m., Sensex was trading at 52,743.38, higher by 544.87 points or 1.04 per cent from its previous close of 52,198.51. It opened at 52,494.56 and has touched an intra-day high of 52,774.47 and a low of 52,471.23 points. Nifty50 was trading at 15,792.45, higher by 160.35 points or 1.03 per cent from its previous close. Manish Hathiramani, technical analyst with Deen Dayal Investments said: "The index took good support at the 15,600 level and has bounced from there. 15,800-15,900 is an area of resistance." "If we can get past that, the markets should resume its endeavour to scale higher towards 16,000-16,100. Until then we continue to be in sideways patch with 15,600 at the lower end and 15,900 at the upper end." On the Sensex, Bajaj Finance, Tata Steel and Titan Company were the top gainers so far, while the only losers were Asian Paints and Nestle India. /IANS