Japan logged its worst ever monthly trade deficit in January despite an upturn in exports as the yen's recent sharp drop pushed fuel costs higher, official data showed Wednesday.

The world's third-biggest economy is mired in recession and a mood of optimism in the stock market and among analysts has so far failed to translate into good macro-economic figures.

The finance ministry data showed Japan suffered a shortfall of 1.63 trillion yen ($17.4 billion) in January, the worst deficit on record for a single month, exceeding the previous record of 1.48 trillion yen for the same month last year.

Comparable data began in 1979. Japan tends to post bad trade figures in January, with exports stalling because of New Year holidays.

Economists on average had expected a shortfall of 1.3 trillion yen. Taro Saito of the NLI Research Institute said the deficit did appear "a lot worse than I had expected".

"Overall, you can't make the deficit go away that easily," Saito told Dow Jones Newswires, adding that Japan would likely see deficits over the coming months.

January exports increased 6.4 percent from a year earlier to 4.8 trillion yen, the first rise in eight months on higher shipments of automobile parts and other items.

But imports rose 7.3 percent to 6.43 trillion yen, boosted by heavier bills for petroleum products, natural liquefied gas and crude oil.

Japan's fuel imports have risen since the 2011 earthquake and tsunami disaster sparked the world's worst nuclear accident in a generation, sending most atomic power plants offline.

But the cost of imported fuel, which is denominated in US dollars, has risen for Japan as the yen has tumbled over the past few months, driven by expectations of aggressive monetary easing under Prime Minister Shinzo Abe.

The dollar's average rate during January was 86.93 yen against 77.33 yen a year earlier, according to customs data, meaning the yen was 12.4 percent cheaper on year.

A lower yen is good for Japanese exporters but there have been accusations in recent weeks, particularly in Europe, that Tokyo is deliberately trying to manipulate currency rates.

The yen was trading around 93.70 to the dollar early Wednesday.

Yoshiro Sato, economist at Credit Agricole, said "the huge deficit at the beginning of the year is, as we expect, likely to result in the annual trade balance remaining in deficit for the third straight year in 2013."

But he said the latter half of the year is likely to see a narrowing deficit on the back of recovery in global demand.

Analysts had expected a boost in exports in January due to the yen's sharp decline and a recovery in trade with China, Japan's largest trading partner.

Exports to China rose 3.0 percent in January with emotions over a territorial dispute easing.

The row sparked huge anti-Japan protests across China and a consumer boycott that weighed heavily on China sales of well-known Japanese brands, including those of top automakers Toyota, Nissan and Honda.

US-bound exports soared 10.9 percent on strong shipments of automobiles and their parts.

Exports to the European Union sagged 4.5 percent, narrower than double-digit plunges in the past months.