Beijing on Thursday began publishing real-time air quality data on the Internet, bowing to a vocal online campaign for greater government transparency over pollution in China's capital.

The move followed the announcement that Beijing would change the way it measures air quality this month to include the smaller particles experts say are most harmful to health, after considering the wishes of residents.

It is the latest example of the challenge authorities face as China's online population -- the largest in the world at more than half a billion -- increasingly uses the Internet to press its demands.

Beijingers have used China's hugely popular microblogging sites to express strong criticism of the city government's data, which frequently rates the air quality as good, even when there is thick smog.

The controversy has been compounded by US embassy statistics on air quality published online and on Twitter that measure the small particles, known as PM2.5, and often register dangerous pollution levels.

The new hourly statistics, available at www.bjmemc.com.cn, will initially be based on the old system, which measures particulate matter under 10 micrometers in size, known as PM10.

Previously, the government released air quality data only once a day, reflecting an average of the previous 24-hour period, while the US embassy in Beijing -- one of the world's most polluted cities -- provides hourly data.

The Beijing Municipal Environmental Monitoring Centre said the change was in response to the demands of the public, which has accused the authorities of deliberately understating the scale of the problem.

"There is a relatively large gap between citizens' actual feelings and the 'past-tense' data," deputy director Zhao Yue told the official Xinhua news agency.