The Purchasing Managers Index of China's non-manufacturing sector, a key economic indicator, dropped 2.6 percentage points to 53.7 percent in September, an official survey showed on Wednesday.

The decline indicated the non-manufacturing economy slowed, said Cai Jin, vice chairman of the China Federation of Logistics and Purchasing, which released the data. A PMI reading above 50 percent indicates expansion from the previous month, while readings below this mark indicate contraction.

A weakening producer service sector was the main reason behind the September decline, he said, but adding that the non-manufacturing economy will keep moderate growth and play its role in stabilizing and restructuring the economy.

The figure followed Monday's release of the manufacturing sector PMI, which continued to contract in September but the rate of deterioration eased slightly than in the previous month.

The country's economy rose 7.6 percent in the second quarter of the year, the slowest rate in more than three years after the global financial crisis.

Analysts expect China's economy to slow further in the third quarter as the European sovereignty debt crisis sags export and a flagging property market dampens investment.

In September, the sub-index for new orders of the non-manufacturing sector decreased by 0.9 percentage point month on month to 51.8 percent, the CFLP data show. The sub-index for new export orders in the non-manufacturing sector hit 49.8 percent, up 0.2 percentage point from the previous month.

To bolster the flagging economy, the country has introduced a slew of pro-growth measures, including more aggressive tax cuts, issuing subsidies to support technological upgrades and opening state-run sectors to private investors.

The CFLP's non-manufacturing PMI is based on a survey of about 1,200 companies in 27 industries, including transportation, real estate, catering and software development.