BEIJING, Sept. 11 -- China's courier sector continued to expand in August, with steady growth in delivery volume, according to an industry index released by the State Post Bureau on Thursday.

The express delivery development index stood at 424.9 in August, up 4.4 percent from the same period last year, according to the bureau.

Broken down, the sub-index for development scale rose 11.2 percent year on year, while the sub-index for development trend increased 10.4 percent from a year earlier.

Last month, China's express delivery industry accelerated the development of its air network and forged closer integration with upstream and downstream sectors, providing robust support for stable economic performance, the bureau said.

The index is compiled based on data from major logistics firms operating delivery services. It reflects overall business activities and trends in the country's courier sector.