The report also showed that total housing inventories at the end of May fell 3.5 percent to 3.80 million existing homes available for sale. This represents 9.6 months of supply at the current sales pace, down from 10.1 months of supply in April.

NAR added that the national median existing home price for all housing types was $173,000 in May, down 16.8 percent from a year earlier. Distressed properties continue to downwardly distort the median price, the group said.

The Commerce Department is scheduled to release a separate report on new home sales in the month of May on Wednesday, with the report expected to show that new home sales rose 2.3 percent to an annual rate of 360,000 units.