Chinese oil giant Sinopec, Asia's largest refiner by capacity, says third-quarter net profit fell 9.4 per cent from a year earlier due to a lower contribution from its chemicals business.

Sinopec reported a net profit of 18.33 billion yuan ($2.82 billion) for the three months ended September 30, a 1.89 billion yuan drop from 20.22 billion yuan in the same period last year.

The decline was "mainly due to plummeting results of the chemicals segment which resulted from changes in the chemical market and demand", the company said in a filing to the Hong Kong Stock Exchange.

Sinopec reported a refinery throughput of 4.39 million barrels a day in the first nine months of the year, up from 4.37 million a year earlier.

"We have ... accelerated an upgrade in the quality of oil products, and adjusted the product mix to increase the output of gasoline and jet fuel," the company said.

The company reported 12.2 billion yuan in exploration expenses for the first nine months, a 31 per cent increase from the previous year.

It said it was focused on achieving growth in reserve and production volume, as well as enhancing exploration in key areas.