Residents across northern China battled through choking pollution on Tuesday, as air quality levels rose above index limits in Beijing amid warnings that the smog may not clear until Thursday.
Visibility was reduced to around 200 metres in the centre of the capital, where mask-wearing pedestrians made their way through a murky haze, despite warnings from authorities to stay indoors unless absolutely necessary.
In a Beijing city office visited by AFP, up to 20 workers wore gas-mask style protective headgear at their desks, and the cloud of pollution shrouded large swathes of the country for the second consecutive day.
State broadcaster China Central Television (CCTV) showed vehicles using full headlights in mid-morning to light a way through the smog, mainly in the badly affected central province of Henan.
A total of 109 flights were cancelled at Zhengzhou Airport in Henan, said CCTV, adding that the haze would last until Thursday.
In the eastern province of Shandong, almost 2,000 passengers were stranded at Qingdao's main airport after it shut with 20 flights cancelled as visibility dropped to 100 metres, according to the Xinhua news agency.
It is at least the fourth time a dense cloud of haze has descended on northern China this winter, with even state media repeatedly expressing anger over the issue.
The China Daily reiterated its calls for firm action on Tuesday, directing them at the capital's newly-installed mayor Wang Anshan, who formally took over on Monday.
"What do Beijing residents expect of their new mayor?" asked the newspaper in an editorial. "Of all the things that need improving, cleaner air will be at the top of many people's wish list."
Wang was quoted by the official Xinhua news agency as saying: "The current environmental problems are worrisome."
The US embassy's air quality index (AQI) reading for Beijing stood at 475 and "hazardous" at 12pm on Tuesday, after having reached 517, or "beyond index", at 6am.
The index rates a reading over 150 as "unhealthy", above 300 as "hazardous", while anything over the upper limit of 500 is regarded as "beyond index".
Meanwhile, the Beijing Municipal Environmental Monitoring Centre gave the figure as 414 at noon, indicating the capital's air was "severely polluted".
The toxic air follows an extreme bout of pollution earlier this month, peaking on January 13 when state media said readings for PM 2.5, particles small enough to deeply penetrate the lungs, reached 993 micrograms per cubic metre, almost 40 times the World Health Organization's recommended safe limit.
At the height of the smog, many residents rushed to buy facemasks and air purifiers, and doctors at two of Beijing's major hospitals said the number of patients with respiratory problems had increased sharply during the period.
China's pollution problems are blamed on the country's rapid urbanisation and dramatic economic development.
But experts have raised questions over China's will and ability to tackle car and coal use, which are seen as key causes of the phenomenon.
Explore further: Beijing choked by third day of hazardous smog (Update 2)