Chinese oil giant Sinopec's annual net profit for 2012 fell 12.8 year-on-year, the firm said, with high crude-oil costs and a slowdown in the global and Chinese economy weighing on its bottom line.

Asia's largest refiner by capacity said in a filing late Sunday to the Hong Kong stock exchange that its net profit for the year fell to 63.88 billion yuan ($10.3 billion) from 73.23 billion yuan in 2011.

Sinopec's filing added that its revenue rose to 2.79 trillion yuan, an 11.2 percent increase from 2011's 2.51 trillion yuan, but operating expenses rose 12 percent for the year, with a 16.4 percent increase in exploration expenses.

"The world witnessed difficult macroeconomic conditions in 2012 as well as a complex and volatile environment in the petroleum and petrochemical market," Sinopec chairman Fu Chengyu said in a statement.

Sinopec said though international prices for crude oil fluctuated for the year, they were able to narrow losses due to China's price adjustments for gasoline and diesel and "rapid growth in domestic demand for gasoline".

The company's refining throughput in 2012 increased by 1.8 percent to 221.31 million tonnes of crude, and it said it plans to refine 238 million tonnes this year.

Sinopec rival PetroChina, the nation's largest listed oil company, on Thursday said its 2012 net profit fell 13.3 percent also due to a slowdown in the growth rate of the Chinese economy, despite increased production.

The Chinese economy expanded 7.8 percent in 2012, its worst performance in 13 years, due to weakness at home and in key overseas markets after the nation saw a growth of 9.3 percent in 2011 and 10.4 percent in 2010.