Service activity at China's private and export-oriented firms improved slightly in May, giving new evidence that the recovery of the world's second-largest economy remains fragile.

HSBC China Service Purchasing Managers Index, a gauge of non-manufacturing activity at mainly private and export-oriented enterprises, stood at 51.2 in May, nearly flat with April's 51.1, the lowest reading since August 2011, HSBC Holdings Plc and Markit Economics said today.

A reading of 50 or higher indicates the activity is expanding.

The latest PMI indicates that China's service sector activity stabilized in May. "A soft patch in manufacturing growth continues to weigh on this industry and adds more downside risks to China's growth rate in the second quarter," said Qu Hongbin, chief economist for China at HSBC.