China Petrochemical Corporation (Sinopec), China's largest oil refiner, reported Wednesday a lower net profit in the first three quarters of this year.

Net profit attributable to shareholders stood at 43.28 billion yuan (about 6.13 billion U.S. dollars) in the first nine months, down 27.8 percent year-on-year, the company said in a report filed with the Shanghai Stock Exchange.

Operating revenue increased 7.7 percent to 2.23 trillion yuan in the period.

Output of refined oil reached 119.5 million tonnes, up 2.9 percent year-on-year while sales stood at 192.4 million tonnes, increasing 8.5 percent.

"While the domestic demand for refined oil products maintained steady growth, the market witnessed strong competition with abundant supply," the report said.

The company said it would pay more attention to market expansion and cost reduction.