BEIJING—China's better-than-expected trade figures in December have sparked questions over whether trade flows have been inflated by investors evading capital controls and the extent of incentives being offered by government agencies to prop up exports.

China reported Wednesday that exports in December declined 1.4% year on year. This was much better than the 8% drop expected by economists in a survey by The Wall Street Journal and compared with a 6.8% decline in November, allowing Beijing to end the trading year on a stronger note. Imports fell by 7.6% last month, better than the expected 11% decline, compared with an 8.7% drop in November.

The December trade figures also were helped by favorable comparisons with year-earlier figures, economists said.

Of particular note was a 64.5% jump in China's imports from Hong Kong, the strongest pace in three years, analysts said. This compared with a 6.2% decline for the January-November period.