BEIJING-- Air China, the country's largest international carrier, said Friday that its net profits fell 13.44 percent year-on-year to 4.06 billion yuan ($634.87 million) in the first half of the year due to high fuel costs.

Its revenue stood at 45.13 billion yuan during the period, up 31.55 percent from a year earlier, the state-owned carrier said in a filing to the Shanghai Stock Exchange.

High oil prices have greatly reduced the carrier's profits as its fuel costs surged 51.41 percent year-on-year to total 5.36 billion yuan over the past six months, the carrier said.

Due to declining demand in the global cargo transportation market, the carrier's cargo and mail transportation sector edged up slightly at 4.76 percent year-on-year to reach 570,400 tons in the first half, with its cargo load factor shrinking 0.67 percent to 58.53 percent.

The carrier also noted that domestic travel demand remained robust. Its domestic routes carried 28.82 million passengers in the past six months, up 33.58 percent from a year earlier, with the passenger load factor rising 4.35 percentage points to 82.43 percent.

Meanwhile, its foreign exchange gains saw a year-on-year rise of 428 percent, or 1.2 billion yuan, during the period on the back of a stronger yuan, the carrier said.

On its outlook for the second half, Air China said it will increase marketing efforts in international markets and improve its cost structure to cope with the pressures of rising oil prices.

Earnings per share stood at 0.33 yuan in the first six months, down 19.51 percent from a year earlier, while its total assets rose by 5.8 percent to 164.22 billion yuan.