Authorities in Beijing have pledged to improve the way they measure air quality amid accusations they massively underestimate pollution in the Chinese capital, state media said Wednesday.

Thick smog that blanketed the city on Monday and Tuesday highlighted a huge discrepancy between official data ranking the pollution at the time as "slight" and US embassy measurements ranking Beijing's air quality as "hazardous".

With growing numbers of Beijing residents trusting the American figures over their own government, the popular state-run Global Times newspaper said city authorities were considering overhauling their own measuring system.

"The Beijing bureau applies the current national standard, which is undergoing an amendment," the Global Times quoted Beijing Municipal Environmental Protection Bureau's Du Shaozhong as saying.

The discrepancy is because China currently only measures large particles that pollute the air, while the US system also includes the smaller particles that make up much of the pollution in Beijing, the paper said.

China currently measures particulate matter between 2.5 and 10 micrometres (393.7 microinches) in diameter, known as PM10.

Scientists say Beijing's pollution is mostly caused by fine particulates smaller than 2.5 micrometres, or PM2.5, which are considered more dangerous to human health.

"Technically we are ready to adopt the PM2.5 standard," Du said on his microblog site.

International organisations including the United Nations list Beijing as one of the most polluted cities in the world, mainly due to its growing energy consumption, much of which is still fuelled by coal.

The discrepancy between the two sets of figures has sparked a debate in Chinese media and among web users, with some saying they suffered from headaches and nausea and disputing the government's assessment of the pollution as "slight".

The Global Times on Monday urged the government to "be cooperative in avoiding confusing information" about air pollution.

"Figures by some local governments show the air pollution index is dropping in some cities, such as Beijing... But some Beijing citizens complain the figures do not match their experience," it said in an editorial.