Applications for U.S. home mortgages slumped for a third week in a row last week, hit by a drop in demand for refinancing, an industry group said Wednesday.

The Mortgage Bankers Association said its seasonally adjusted index of mortgage application activity, which includes both refinancing and home purchase demand, tumbled 11.7 percent in the week ended Nov. 25.

The MBA's seasonally adjusted index of refinancing applications dropped 15.3 percent, the biggest decrease in more than a month. The gauge of loan requests for home purchases dipped 0.8 percent.

The refinance share of total mortgage activity eased to 73.9 percent of applications from 75.9 percent.

Fixed 30-year mortgage rates averaged 4.21 percent in the week, down 2 basis points from 4.23 percent the week before.

The survey covers over 75 percent of U.S. retail residential mortgage applications, according to MBA.