Pending sales of previously owned U.S. homes unexpectedly rose in April to the highest level in six months as foreclosed properties flooded the market and drove prices sharply lower, a real estate trade group report showed.

The National Association of Realtors Pending Home Sales Index, based on contracts signed in April and seen as a key barometer of future housing activity, increased 6.3 percent to 88.2 from an unrevised 83.0 in March.