Sensex tanks 537 points on rout in China markets: The S&P BSE Sensex tumbled 537 points to end below its crucial psychological level of 26,000 in trade, while broader CNX Nifty also settled below its key support level of 7,800. Domestic markets slipped tracking weak trend seen in Asian markets after data on Friday showed China's factory activity shrank for a 10th straight month in December. Reacting to the news, China's benchmark CSI300 share index dipped 7 per cent on the first session of 2016, prompting the stock exchange to halt trading for the rest of the day.