Extending their weakness, the domestic stock markets opened weak, and the Sensex at the Bombay Stock Exchange had later declined 267 points, or 0(point)8 percent, to 31,266, a short while ago. The Nifty at the National Stock Exchange had dropped 87 points, to 9,734.Other key Asian markets in China, Hong Kong, South Korea and Singapore had lost between 1.1 percent and 2.1 percent.At the forex market, the rupee had depreciated 3 paise, to 64.12 against the dollar in afternoon deals.