The Norwegian government's statistics office said the total sale of all petroleum products from the country declined in September.

Statistics Norway said total sales of petroleum products from Norway in September amounted to 4.5 million barrels of oil equivalent.

"This equals an 8.9 percent decrease compared to September 2014," the agency said. "Sales of all petroleum products decreased."

Sales figures relate primarily to auto fuels. The statistics office said the value of total crude oil exports from Norway were down 11.4 percent from August to September and 42.5 percent lower year-on-year. Gas sales from August were down 3.7 percent in value, but up 34.3 percent year-on-year.

Norway is a main supplier of oil and natural gas to the European economy. The latest production figures from the Norwegian Petroleum Directorate, the nation's energy regulator, show an average daily production of around 1.9 million barrels of oil, natural gas liquids and condensate.

Economic growth has been slow for most of the year for Norway, with gross domestic product increasing by slightly less than 1 percent for the last four quarters combined.

Statistics Norway said the trade surplus for September was $1.9 billion, the second lowest level since March 2003.

Norge Bank, the country's central bank, said a weakened value of its currency, the krone, could make exports more attractive, though the overall economy is expected to falter and unemployment is projected to rise. The government's statistics office said the decline in investment in the petroleum industry is one of the key factors dragging on the Norwegian economy.