China National Offshore Oil Corporation Ltd -- the country's largest offshore oil producer -- has seen its half-year net profits fall 19 percent to 31.87 billion yuan ($5.02 billion).

The declining demand for crude oil in global markets as well as the economic downturn hit the company's profitability, CNOOC said in its half-year report, filed with the Hong Kong Stock Exchange.

Despite the 19 percent year-on-year fall, the oil giant remains one of the most profitable companies in the country. It posted record-high net profits of 70.26 billion yuan for the whole of 2011.

In the first half of this year, oil and gas revenues dipped 1.4 percent from a year earlier, to 95.66 billion yuan, the Hong Kong-listed company said.

Oil and gas output totaled 160.9 million barrels, down 4.6 percent year-on-year. That was a result of an oilfield in China's Bohai Bay being suspended because of an oil leak. The drop was also due to maintenance of oilfields and the sale of interests in a block in Indonesia.

The company's earnings per share also went down 19 percent to reach 0.71 yuan, while the board of directors proposed a half-year pretax dividend of HK$0.15 pending the approval of shareholders.

The company's average oil price stood at $116.91 per barrel and the average natural gas price reached $5.9 per 1,000 cubic feet, representing year-on-year increases of 8.1 percent and 20 percent, respectively. The company aims to meet its annual production target of between 330 million and 340 million barrels of oil equivalent.