State-owned PetroChina has overtaken ExxonMobil as the world's biggest publicly-traded producer of oil, according to figures provided by the Hong Kong-listed firm on Thursday.

The news comes as energy-hungry China increases its strategic oil reserves, amid global uncertainties surrounding oil-producing countries such as Iran and rising prices.

PetroChina said its oil production reached 886.1 million barrels in 2011, the equivalent of around 2.43 million barrels per day (bpd), while the US energy titan produced around 2.3 million bpd last year.

This compares to 2.35 million bpd for PetroChina in 2010 -- smaller than Exxon's 2.42 million bpd that same year.

The Chinese energy firm said last year's increase was driven largely by efforts to ramp up production in new oilfields in the country.

"Major development indicators of the existing oilfields continued to improve... which further strengthened the basis for the stable production of existing oilfields," PetroChina said in a statement.

Julian Jessop, commodities economist at Capital Economics, said the news did not come as a surprise because the US oil market is more fragmented than in China, with more producers competing against each other.

"If you look at total oil production, the US is still quite a long way away, and produces twice as much as China does," he said.

PetroChina earned net profit of 132.96 billion yuan ($21 billion) in 2011, down five percent from a year ago. The figures were well below a Dow Jones poll of analysts who were expecting an average 138.58 billion yuan.

Revenues for 2011 came in at 2.04 trillion yuan, up 36.7 percent over the previous year.

Oil prices have traded mostly above $100 a barrel in recent months on worries over ongoing tensions between Western nations and major crude producer Iran.

Despite experiencing an economic slowdown, China's thirst for oil is likely to remain the same.

"Even if the economy slows, Chinese demand is probably not going to drop that much because it might be that the additional oil they import is added to reserves rather than used for current consumption," Jessop said.

"So the pressure on companies like PetroChina to source more oil from wherever they can is going to remain very strong as well."