China, Australia's biggest trade partner and a major buyer of its commodities, reported a surprising jump in August imports, showing a strengthening of domestic demand in an economy that has become a major driver of global growth.

The country's imports posted a 35.2 percent year-on-year increase to reach $119.27 billion last month, with the growth rate up 12.5 percentage points from that in July, the General Administration of Customs (GAC) said Friday.

This easily beat July's 22.7 per cent rise and market forecasts of a 26.1 per cent increase.

Annual export growth, meanwhile, slowed to 34.4 per cent in August from 38.1 per cent in July but was close to expectations of a 35 per cent rise.

As a result, the monthly trade surplus is narrowed to $US20 billion in August from $28.7 billion the previous month. The median forecast was $US27.1 billion.

The surge in imports, which reduced China's politically sensitive trade surplus, came ahead of US Congressional hearings next week on whether to punish Beijing for what many in Washington see as an unfairly undervalued yuan.

Before today's release, Ken Peng, a Beijing-based economist at Citigroup said, ''With the yuan appreciating very slowly and US mid-term elections drawing near, it's inevitable that Sino-US tension will heat up again.''