Hong Kong's exports grew 15.2 percent year-on-year in September, the government said Thursday, while warning of an economic outlook fraught with challenges.

The value of total exports rose to HK$313.2 billion ($40.4 billion), with total exports to Asia up 20.1 percent, the Census and Statistics Department said. August saw only a marginal 0.6 percent increase in exports year-on-year.

Imports rose 14.9 percent from a year earlier to HK$358.3 billion, compared to a 0.9 percent increase in August year-on-year.

A trade deficit of HK$342.9 billion was recorded for the first nine months of 2012.

A "distinctly low base of comparison in the same month of last year" and "some improvements in such major markets as the mainland (China) and the US" contributed to the growth, a government spokesman said in a statement.

"The global economic environment is still fraught with downside risks stemming from the euro debt crisis and looming US fiscal cliff," he added.