Japan's current account surplus shrank 64.3 percent year-on-year in August, the sixth straight monthly fall as higher energy import costs overshadowed a small gain in exports, data showed Tuesday.

Higher oil prices and utilities' boosting of liquefied natural gas imports to compensate for the shutdown of the majority of Japan's atomic reactors after the March Fukushima crisis helped push Japan's trade balance into a deficit.

The surplus in the current account, the broadest measure of Japan's trade with the rest of the world, stood at 407.5 billion yen ($5.3 billion) in August before seasonal adjustment, finance ministry data showed.

The result, the sixth consecutive drop in the aftermath of the March 11 earthquake and tsunami, was lower than expectations of a 446.9 billion yen surplus in a survey of economists by Dow Jones Newswires and the Nikkei.

Exports rose 4.0 percent in August on-year, the first gain since the disasters that left 20,000 dead or missing, sparked the Fukushima atomic crisis and ravaged crucial component supply chains, massively disrupting industry.

But imports jumped 22.4 percent, partly due to higher oil prices and Japan's increased need for fossil fuels.

In August, Japan saw a trade deficit of 694.7 billion yen, from a surplus of 170.6 billion yen a year earlier.

Analysts warn the current account surplus is expected to continue to decline as Japan's recovery from recession may slow amid concerns about the health of the global economy and the impact of a strong yen on the nation's exporters.

Japanese companies have worked to quickly to restore quake-hit production levels but there are concerns a strong currency could undermine them.

"Although exports rose in August, the gain was still too weak to declare a full recovery," said Hideki Matsumura, a senior economist at Japan Research Institute.

"It is hard to expect a full recovery in exports for the time being," Matsumura said.

"This weak trend in the current account is likely to continue until the April-June quarter, exactly a year after the East Japan Earthquake," he added.

Analysts also said the outlook for Japan's exports may not bode well given the strong yen, which is still hovering near a record high against the dollar.

A strong domestic unit erodes repatriated profits and has prompted fears more firms will move production overseas in search of cheaper labour costs.

"We have to pay close attention to exports, which could be dented further if the yen remains strong," Norio Miyagawa, senior economist at Mizuho Research and Consulting, told Dow Jones Newswires.

"Weaker exports would mean more downside risks for Japan's economic recovery," Miyagawa said.

The dollar was around 76.66 yen early Tuesday, just off its record low of 75.94 yen marked in August and much lower than the average 81.15 yen that large manufacturers have set for their business plans for the current fiscal year.

The current account measures trade in goods, services, tourism and investment. It is calculated by determining the difference between Japan's income from foreign sources against payments on foreign obligations, and excludes net capital investment.