US housing prices are showing signs of recovery after a slide that sent values to levels last seen in 2003 and left almost a quarter of homeowners with properties worth less than their mortgages.

The S&P/Case-Shiller index of home prices in 20 cities rose 0.6% in February from a year earlier, the first annual gain since December 2006, the group said yesterday. The National Association of Realtors reported last week that existing-home prices advanced 0.4 percent in March as sales climbed for the first time in four months.

“We’ve turned a corner with housing, though it’s hard to see any robustness,” said economist Karl Case, who with Robert Shiller created the S&P/Case-Shiller index. “Prices could fall further, but as long as mortgage rates don’t jump and employment continues to improve, we should see housing play a key role in preventing a double-dip recession.”