SINGAPORE, July 25 (Reuters) - Singapore private home prices were almost unchanged between April and June, rising just 0.2 percent, the third straight quarter of slower growth as economic concerns ended a four-year housing boom, data showed on Friday.

The Urban Redevelopment Authority (URA) said the price index for private homes, an indicator of inflation holding at 26-year highs, rose to 177.5 for the three months ended June from 177.2 in the previous three-month period.

Prices rose 3.7 percent in the first quarter of 2008, after soaring 31 percent in 2007 amid a housing boom fueled by strong growth in the Singapore economy and by property speculators.

But an uncertain economic outlook and a looming housing glut has threatened to plunge the property market into a prolonged downturn, which could deal a blow to top builders such as CapitaLand , Keppel Land and City Developments .

Sales volume sank to a five-year low in the first quarter of 2008 as government moves to curb property speculation took effect and global economic fears kept buyers at bay.

Second quarter sales more than doubled to over 1,500 units as more projects were launched while some developers cut prices, but volumes are still less than a third of the units sold in the same period last year.