Japan on Wednesday posted its worst April trade deficit as a weak yen ramped up import costs and helped extend the run of monthly shortfalls to the longest in more than three decades.

Data from the finance ministry showed Japan incurred a trade deficit for the 10th straight month in April with the red-ink expanding a worse-than-expected 69.7 percent on year to to 879.9 billion yen ($8.6 billion).

Trade data is a closely watched indicator of Prime Minister Shinzo Abe's progress in firing up Japan's export-led economy.

Expectations for Abe's pro-growth, pro-spending policies have weakened the yen more than 20 percent against the dollar over the past six months and boosted share prices to their highest level in more than five years.

But the latest data could be a sign that a rebound in exports has yet to outweigh higher imports on the back of a weaker yen and greater energy needs.

The deficit was the biggest for the month of April in comparable official data that goes back to 1979 and was also worse than an average shortfall of 620 billion yen forecast by economists polled by the Nikkei business daily.

It was also the longest run of monthly deficits since a 14-month string from July 1979 to August 1980.

"Exports may recover further but because import costs are rising quite a bit, trade deficits will likely continue," said Junko Nishioka, chief economist at RBS Securities Japan.

The latest set of figures indicated that the "worst period" is over for exports, she said.

The data did not damp enthusiasm for Japanese shares with the benchmark Nikkei stock average gaining 1.00 percent by mid-morning.

In April exports rose 3.8 percent to 5.78 trillion yen while imports jumped 9.4 percent to 6.66 trillion yen.

The yen's average rate was 96.01 to the dollar in April against 82.31 a year ago, meaning the value of the Japanese currency fell by nearly 17 percent on year, the ministry data showed.

A lower yen helps Japanese exporters but pushes up import bills.

Higher import costs have been resulting in higher materials and parts prices, which are leading to higher retail prices of various items ranging from foodstuff to laptops.

With the yen hitting multi-year lows against the dollar, some politicians have started voicing concerns over its negative impact on people's lives.

Japan's fuel imports have also stayed high as most of its nuclear reactors remain off-line since the huge earthquake and tsunami in 2011 sparked the world's worst atomic accident in a generation.

By region, US-bound exports in April jumped 14.8 percent to 1.10 trillion yen, the highest figure since October 2008, on the back of strong shipments of automobiles.

Japan's surplus with the United States soared 32.5 percent to 563.0 billion yen while Japan suffered a trade deficit of 38.6 billion yen with the European Union as exports there kept falling.

With China, Japan's deficit expanded by 60.2 percent to 442.5 billion yen as exports rose only 0.3 percent on a slowing of growth in China's economy and as political tensions between the two countries continue to weigh on sales of Japanese goods there.

-- Dow Jones Newswires contributed to this article --