The Chinese government has stepped up efforts to make data on the country's air quality more transparent, including opening up pollution-monitoring centres to public observation.

It is a rare bow to public pressure, as many citizens have been complaining of highly under-reported rates of pollution.

Many experts say the government has not taken enough steps to fight the "hazardous" problem, caused mainly by the widespread usage of fossil fuels for energy.

China, home to around 1.3 billion residents, is the world's largest coal producer in the world.

Melissa Chan reports from Beijing.