BEIJING, March 28 -- China National Offshore Oil Corporation (CNOOC), the country's third-largest oil producer, on Friday reported a net profits decline in 2013 due to low oil prices and high operating costs.

The company raked in 56.5 billion yuan (9.1 billion U.S. dollars) in net profits last year, 11.4 percent less than in 2012, according to its financial report.

CNOOC's oil and gas production stood at 411.7 million barrels of oil equivalent, up 20.2 percent from the previous year. The production included 60.8 million barrels from the acquisition of Canada's Nexen Inc.

The company's sales revenue was 226.4 billion yuan last year, up 16.3 percent. But its exploration costs and production costs surged by 89.3 percent and 40 percent, respectively.