US home prices climbed in April but gains moderated at the start of the spring home-buying season, according to the S&P/Case-Shiller index published Tuesday.

Although the 20-city price index rose 1.1 percent in April, following a 0.9 percent rise in March, the year-over-year price gains advanced 4.92 percent, a slightly slower pace than in the prior month.

"Home prices continue to rise across the country, but the pace is not accelerating," said David Blitzer, managing director and chairman of the index committee at S&P Dow Jones Indices.

Nine cities had accelerating price increases, while gains slowed in 11 cities, including Boston and Miami.

Denver and San Francisco showed the strongest year-over-year gains, with prices up 10.3 percent and 10.0 percent, respectively.

"Recent housing data is positive. Sales of new and existing homes are rising in recent reports and construction of new homes enjoyed strong gains in May," Blitzer said.

Ian Shepherdson of Pantheon Macroeconomics said the report appeared to be an outlier in otherwise better housing data.

"The underlying trend is much stronger than this report seems to suggest, and with sales rising amid very tight inventory, we have to expect faster increases again once the weather hit washes fully through the data," he said.