China's imports and exports slumped again in August, authorities said Tuesday, the latest setback for the world's number-one trader in goods as weakness reverberates through the global economy.

Fears of a slowdown in Chinese growth have sent panic through world stock exchanges, as the country is a key driver of global expansion and a vital market.

But its falling demand for commodities has hammered prices and resource-driven economies such as Australia.

At the same time China is being hit by weaker demand from the EU, its biggest trading partner, and Japan -- whose economy is shrinking -- reducing the amount it earns from exports.

The European Union Chamber of Commerce urged Beijing to accelerate modernisation, warning in an annual report that "slow" implementation of market reforms risked plunging the country into stagnation.

Beijing is trying to rebalance to a more sustainable economic model where expansion is predominantly driven by domestic consumer demand rather than exports and investment, but the transition is not proving easy.

"Globally everyone has had a very, very weak period of exports and economic growth," Jefferies Group strategist Sean Darby told Bloomberg News.

"It's not just China, but also Taiwan, Korea, and most of Asia and emerging markets. China gets the focus because it's the biggest, but in reality, no one is having a very good time out there."

Chinese authorities are targeting year-on-year growth of around six percent in two-way trade this year. Instead it fell by 9.1 percent overall in August, measured in dollar terms, Customs said.

"Exports to the US and the Association of South-East Asian Nations continued to grow but shipments to the EU and Japan declined," Customs said on its website.

Exports fell 5.5 percent year-on-year to $196.9 billion in August, it said.

The drop, though, was significantly less than the median forecast of a 6.6 percent decline in a survey of economists by Bloomberg News, and also an improvement from July's 8.3 percent fall.

Imports fell 13.8 percent year-on-year to $136.6 billion, customs said, attributing the decline to widespread commodity price falls.

It was the 10th consecutive monthly fall in import values, and worse than both the Bloomberg survey's projection of a 7.9 percent decline, and July's 8.1 percent drop.

China's trade surplus was $60.2 billion last month, customs said, without giving the change in dollar terms. It earlier said that measured in China's yuan currency the surplus had risen 20.1 percent.

- 'Very unsettling' -

But Shanghai stocks closed up 2.92 percent despite the data, with Hong Kong also rising strongly, surging 3.28 percent. Tokyo, though, slumped 2.43 percent.

There was speculation of state buying in Shanghai, as part of China's broad interventions to try to shore up prices that have slumped nearly 40 percent since mid-June.

Goldman Sachs estimated in a report that Beijing had spent 1.5 trillion yuan ($234 billion) in three months to support the market, and authorities said they planned to suspend trading on the exchanges if they move more than five percent in a day.

Julian Evans-Pritchard of Capital Economics said the outlook was "brighter than many believe".

"The deeper contractions in headline trade growth will undoubtedly be viewed by some as further evidence of a deteriorating economic outlook for China," he said.

"But we think the apparent weakness is misleading," he added, citing a high comparative base from last year for exports and commodity price deflation weighing on imports.

One-off factors such as giant blasts that killed 161 people in the port of Tianjin, and factory closures ahead of a World War II anniversary parade were also involved, he said.

"Trade growth ought to recover over the coming quarters."

Authorities have stepped up efforts to bolster growth, with the central bank last month reducing interest rates for the fifth time since November.

They also lowered the yuan's central rate against the US dollar by nearly five percent in a single week, which should make Chinese exports cheaper on world markets.

The Chinese government is aiming for growth of "around seven percent" this year. Expansion stood at 7.0 percent in each of the first two quarters this year, according to official figures, but on Monday the 2014 growth statistic was lowered to 7.3 percent, from the 7.4 percent announced in January.

Communist authorities have promised to give market forces the "decisive role" in the economy, but in its annual report the European Chamber said China's "markedly slow progress" was "very unsettling for business".

Implementing change has taken on an "urgency with the economy slowing down", its president Joerg Wuttke told AFP.

"It is sometimes disappointing to see how little this derives into real time action.

"It would be terrible if they would waste a crisis. The stagnation of Japan should be a warning of where China could end up."