Japanese exports to China fell again last month as a slowdown in the world's number two economy weighs on the countries' huge trading links, official data showed Wednesday, while shipments to the key US market also stumbled.

The disappointing figures, following a decline a month earlier, highlight the challenges facing Tokyo's bid to kick-start the economy in the face of slowing global growth.

And they will heap pressure on the Bank of Japan ahead of a meeting next week, with speculation building that policymakers are set to announce more stimulus as Japan teeters on the brink of recession.

The value of exports by Japanese firms to China sank 3.5 percent in September, the finance ministry said, while they were also down to other Asian countries.

While export values were up in the key US market and European Union, the volume of US-bound goods weakened.

Japan's exports grew by just 0.6 percent last month, their slowest pace in over year, underscoring global weakness, despite the benefits of a weak yen, which makes the country's exporters more competitive overseas.

On Monday, fresh third-quarter data showed China's economy grew at its slowest rate in six years.

Worries about China have rippled across global equity markets and sown fear about the wider impact on global growth.

"(Japanese) exports are weak across the board and that trend is expected to continue for the time being," said Taro Saito, a senior researcher at NLI Research Institute.

"While exports to Asia and China are weak, more importantly, volumes to the US are slowing."

The latest figures are a red flag ahead of next month's release of third-quarter GDP figures, which follow a contraction in the April-June period.

The International Monetary Fund has cut its growth forecast for Japan while Standard & Poor's recently lowered its credit rating on the country, expressing doubt that Prime Minister Shinzo Abe's plan to fix the economy would work.

Abe has for more than two years pushed a huge spending blitz and monetary easing drive -- called "Abenomics" -- to inject life into the world's number three economy and reverse almost two decades of deflation.

While the scheme showed early promise, with stocks surging and growth advancing, recent weak numbers have raised questions about its effectiveness as consumer prices stagnate and economic growth stalls.

Wednesday's lacklustre trade data may boost speculation that Japan's central bank will expand its record 80 trillion yen ($665 billion) annual asset-buying scheme to counter the downturn.

However, in one bright spot, Japan's overall trade balance was down close to 90 percent from a year earlier as weak energy prices took pressure off the country's import bill.

The trade deficit fell to 114.5 billion yen ($955.6 million) in September, compared with 962 billion yen in the same month of last year.

Energy imports went through the roof after Japan was forced to turn to expensive fossil fuel alternatives when its nuclear plants were shuttered in the wake of the 2011 Fukushima nuclear crisis.