A Chinese woman covers her mouth as she makes her way along a busy intersection in Wuhan, central China's Hubei province on Monday. The Chinese metropolis of Wuhan was blanketed by thick yellowish cloud, raising fears of pollution among its nine million inhabitants, as air pollution is increasingly acute in major Chinese cities and authorities are frequently accused of underestimating the severity of the problem in urban areas, especially in Beijing.

A thick yellow cloud covers a busy intersection in Wuhan, central China's Hubei province, on Monday.

A woman wears a mask as she walks along a street in front of a Chinese temple during a hazy day in Wuhan, Hubei province on Monday. China's carbon emissions could be nearly 20 percent higher than previously thought, a new analysis of official Chinese data showed on Sunday, suggesting the pace of global climate change could be even faster than currently predicted.

The new China Central Television (CCTV) tower hardly visible as fog covers most of Beijing on Saturday. More than 400 flights to and from Beijing airport, including around 35 international services, were cancelled or delayed due to thick fog and strong air pollution covering the city, which the US embassy own measuring system, said pollution in Beijing had reached the "hazardous" level early March 17, before dropping one notch to "very unhealthy" later.

Vehicles make their way along a highway as fog covers most of Beijing on Saturday.

Passengers wait for their flights as almost 250 flights were cancelled, including some 15 international services, while more than 180 flights were delayed, including about 20 international services at the Beijing Capital International airport as visibility was at less than 200 metres (650 feet), official state news agency Xinhua said, blaming "widespread fog" for the disruption, in Beijing on Saturday.