Japanese exports faltered in April after separate figures last week showed the world's number three economy dodged a recession in the first quarter.
A fall in shipments of cars and steel overseas led exports lower, as key producers including auto giant Toyota warned that a rally in the yen was taking a bite out of profits, on the back of a slowdown in China and other emerging economies.
Deadly earthquakes in southern Japan last month forced the temporary closure of some regional factories, weighing on production.
"Exports of US-bound automobiles have rapidly fallen, which could have been an effect of production suspension due to earthquakes in Kumamoto," SMBC Nikko economist Junichi Makino said in a note.
The government has approved a 778 billion yen ($7.1 billion) extra budget in response to the disaster.
On Monday, the finance ministry said exports dropped 10.1 percent last month from a year ago to 5.89 trillion yen, the seventh straight monthly fall.
The value of imports also plunged 23.3 percent to 5.06 trillion yen, mostly due to fluctuations in oil and energy prices, the ministry said.
Japan's trade surplus sat at 823.5 billion yen.
The recent surge of the yen has been a cause of headache to Prime Minister Shinzo Abe's efforts to boost the economy, which expanded by 0.4 percent between January and March after a contraction in the last three months of 2015.
A consumer spending rebound helped drive the better than expected figures, but the leap year added another day of production -- and spending -- to the economy's performance.
Abe's growth plan -- big government spending, central bank monetary easing and reforms to the highly regulated economy -- initially appeared to bear fruit after he came to power in late 2012 elections.
The yen weakened sharply, which boosted Japanese exporters' profits and sparked a huge stock market rally.
But sustained growth has been elusive and Abe's efforts to overhaul the economy have been widely criticised as half-hearted.