US single-family home prices in 20 key urban markets rose in April from a year earlier by the most in over 15 years, a closely watched survey said on Tuesday.

The S&P/Case Shiller composite index of 20 metropolitan areas gained 14.9 percent through the 12 months ended in April, the largest annual price increase since December 2005. A Reuters poll of economists had forecast a 14.5% increase.

On a month-to-month basis, the 20-city composite index rose 1.6 rose from March. Economists polled by Reuters had been expecting a 1.7 percent increase.

Home prices have surged nationwide in large part due to limited supply.

Last week, the Commerce Department reported that sales of new US single-family homes fell to one-year low in May as expensive raw materials such as lumber continue to increase prices of newly constructed houses.