Japan's merchandise trade surplus dropped 9.8 percent in November from a year earlier to 598.5 billion yen, marking the fifth consecutive month of decline, the Finance Ministry said Wednesday.

Exports were up 10.1 percent to 4.28 trillion yen, while imports advanced 14.1 percent to 3.68 trillion yen, the ministry said in a preliminary report.

Both imports and exports rose for the 13th straight month.

A ministry official said the nation's surplus continued its downswing as a rise in imports outpaced that of exports on the back of high crude oil prices.

Crude oil prices in November came to an average $32.4 a barrel -- up 40.3 percent from a year before and the highest since December 1990, when they averaged $32.8 -- and an average 22,015 yen per kiloliter, up 43.9 percent.

"Basically, both exports and imports will likely follow the recent pattern and continue expanding down the track. And the pace of import growth will likely be faster than that of export growth, thus narrowing the trade imbalance to some extent," the official said. Manufactured goods accounted for 61 percent of overall imports.

The yen averaged 108.15 to the dollar in November, down 2.7 percent from a year earlier. In October, the yen's value weakened against the dollar for the first time in 24 months. The politically sensitive trade surplus with the United States strengthened 18.2 percent to 644.1 billion yen, up for the second straight month.

Exports to the U.S. were up 10.3 percent from a year earlier to 1.30 trillion yen and up for the fourth consecutive month. Imports were also up 3.6 percent to 660.3 billion yen for the seventh straight month of increase.

The official said the slower pace of import growth compared with a year before, stemming from a lack of large-scale aircraft imports in the month, magnified Japan's trade surplus with the U.S. Japan's merchandise trade balance, which is reported before adjustment for seasonal factors, is measured on a customs-clearance basis.

The trade surplus with other parts of Asia jumped 16.2 percent to 211 billion yen, after suffering its first fall in seven months in October.

Exports to Asia rose 19.3 percent to 1.8 trillion yen for the 18th consecutive month of expansion, and imports grew 19.7 percent to 1.59 trillion yen, up for the 14th straight month.

The trade surplus with the 15-member European Union amounted to 234.8 billion yen, down 1 percent, for the third consecutive month of decline.

Exports to the EU fell 1.4 percent to 667.6 billion yen for the second straight monthly fall due to the faltering euro, and imports slipped 1.6 percent to 432.8 billion yen for the first downturn in four months.