The Institute for Supply Management's index of nonmanufacturing activity rose unexpectedly in April, reports said.

The index, which measures activity in the service sector, climbed to 50.7 last month from 47.9 in March. A reading above 50 indicates expansion of prices and activity; a reading under 50 points to contraction.

"With the ending of the war in Iraq, purchasing and supply executives report a return to growth in business activity," the ISM reportedly said.

The news gave markets a slight boost in morning trading, as recent economic data have been relatively weak.