U.S. home prices rose 12.4 percent in July compared with a year ago, the most since February 2006. An increase in sales on a limited supply of available homes drove the gains.

The Standard &Poor's/Case-Shiller 20-city home price index improved from a 12.1 percent year-over-year gain in June. And all 20 cities posted gains in July from the previous month and compared with a year ago.

Still, the month-over-month price gains shrank in 15 cities in July compared with the previous month, indicating prices may be peaking.

Home prices soared 27.5 percent in Las Vegas from a year earlier, the largest gain. San Francisco's 24.8 percent jump was the second largest and the biggest yearly return for that city since March 2001.