BEIJING, Oct. 13 -- China's exports saw the fastest growth in 19 months, expanding by 15.3 percent from a year ago to 213.7 billion U.S. dollars in September, customs data showed on Monday.

The September growth rate was the highest monthly export reading since March 2013.

Imports increased 7 percent year on year to 182.7 billion U.S. dollars in the month, and total foreign trade volume rose 11.3 percent to 396.4 billion U.S. dollars, the General Administration of Customs (GAC) said.

September's growth rate in imports also marked the best monthly reading since December 2013, according to GAC.

Trade surplus in September more than doubled from last year to 31 billion U.S. dollars, compared with 49.8 billion U.S. dollars seen in August.

Zheng Yuesheng, GAC spokesman, said China's foreign trade was gaining traction quarter by quarter despite a complex world economy.

The spokesman attributed September's strong growth to a string of government measures adopted in May to stabilize foreign trade, as well as rebounding global demand.

"We hope the strong momentum to continue in the fourth quarter," Zheng said, adding export pressure will lift in the fourth quarter.

The export leading index improved by 1.4 percentage points from August to reach 43.3 percent in September, indicating exporters are more optimistic about coming months, according to GAC.

For the January-September period, China's foreign trade added 3.3 percent year on year to reach 3.16 trillion U.S. dollars, with exports up 5.1 percent at 1.7 trillion U.S. dollars, imports up 1.3 percent at 1.46 trillion U.S. dollars.

Trade surplus in the first nine months expanded by 37.8 percent from previous year to 231.6 billion U.S. dollars.

The European Union (EU) remained China's biggest trading partner, with two-way trade totaling 2.81 trillion yuan (457 billion U.S. dollars) in the Jan-Sept period, up 10.2 percent from a year earlier.

China's trade with the United States, its second largest trade partner, rose 5.2 percent year on year to 2.48 trillion yuan from January to September, while China-ASEAN trade went up 6 percent to 2.13 trillion yuan.

Trade between China's mainland and Hong Kong fell 13 percent to 1.61 trillion yuan in the first nine months.

In contrast to the official optimism, Lu Zhengwei, chief economist of Industrial Bank, was less upbeat while commenting on the trade outlook.

"The rejoice [over exports] will be short-lived and sadness will return soon," Lu warned, predicting a sharp slowdown in exports in the fourth quarter based on the past experience on trade fluctuation.

Previously, the market expected a decline of 2 percent in imports in September and an increase of 12 percent in exports.