BEIJING - Sales revenue of China National Offshore Oil Corp (CNOOC) went down 39.9 percent to 35.5 billion yuan ($5.8 billion) in the first quarter, the company said on Friday.

CNOOC, China's largest offshore oil and gas company, attributed the drop to the falling oil prices.

Oil and gas production in the first quarter went up 9.4 percent to 118 million barrels of oil equivalent, thanks to some new fields going on stream.

The company's average oil price during the period was $53.4 per barrel, down 49 percent. Gas was priced at $6.68 per thousand cubic feet, up 5.5 percent.

CNOOC said its expenditure for the first three months went down 15.7 percent to 15.9 billion yuan as it increased efficiency and lowered costs.