China's state media have called for environmental improvements in unusually frank discussions of the country's pollution problem, as thick smog continues to shroud Beijing and other cities.

Stores sold out of masks and the capital implemented its new pollution emergency response plan for the first time after visibility plummeted at the weekend. Several construction sites were ordered to halt work, factories slowed production and authorities ordered a curb on the use of government cars. Schools cancelled outside activities and authorities advised residents to stay inside.

Hospitals reported increases of up to 30% in the number of patients reporting breathing problems as officials warned that the conditions were likely to last until Wednesday – a day longer than previously predicted – when winds should help to disperse the pollution.

Other areas saw mass flight delays and highway closures on Sunday. Visibility in Changsha, the capital of Hunan, reportedly dropped to 50m.

Beijing's levels are by far the worst recorded since the government began releasing figures on PM2.5 particles – tiny particulate matter thought particularly damaging to health because it can penetrate deep into the lungs – early last year and the US embassy began issuing its own measurements four years ago.

According to an official monitoring centre in Beijing, levels of PM2.5 were well above 600 micrograms per cubic meter in several places on Saturday, and may even have hit 900. Though Monday's level dropped to around 350, that is still far above the safe level of 25 designated by the World Health Organisation.

Pan Xiaochuan, the deputy director of the department of occupational and environmental health at Peking university, said the current problem was caused by weather conditions rather than increased emissions, although some have suggested more people are burning coal due to a particularly cold winter.

He said stricter regulations on emissions were needed in areas around Beijing, but added: "The government responded quickly this time. CCTV [the state broadcaster] news has reported the pollution. It shows the transparency of the government's work has been enhanced. It is a new phenomenon."

State newspapers have run highly critical articles saying more needed to be done to tackle the problem at its source.

"How can we get out of this suffocating siege of pollution?" the People's Daily, the official Communist party newspaper, asked in a front-page editorial.

"Let us clearly view managing environmental pollution with a sense of urgency."

It said around half of more than 70 Chinese cities monitored for air quality showed severe pollution over the weekend.

The populist state-run Global Times newspaper said the problem had triggered public calls to shift development "away from the previous fixation on economic growth", while the China Youth Daily, titled a front-page commentary: "More suffocating than the haze is the weakness in response."

Well known environmentalist Ma Jun said: "Given the public's ability to spread this information, especially on social media, the government itself has to make adjustments."

While Chinese environmental regulations have become far more stringent, environmentalists have complained that officials are often reluctant to enforce standards for fear of holding back economic growth.

But John Cai, the director of the centre for healthcare management and policy at Beijing's China Europe International Business School, warned: "The increased disease burden [due to poor air quality] has caused a serious financial burden on government and individuals.

"The recent serious pollution will send a serious warning to the government and will have an important impact in making the government speed up its regulation and enforcement."

Shops have been unable to keep up with the surge in demand for masks and air purifiers, with many running out.

"[Our] masks were not specially designed to prevent PM 2.5, but they all sold out anyway. We are trying to purchase more," said an assistant at the Fujitang drug store in Beijing.

An employee at the White Pagoda drugstore added: "People didn't come here to buy one or two, but ordered a lot for their friends and family, and companies came here to buy for their staff, too. "

At a Sundan appliances store in central Beijing, sales assistant Ms Jiang said sales of air purifiers had increased roughly ten-fold. The Yuanda Group said it had upped production of the machines because sales had risen recently due to poor air quality throughout China. © Guardian News and Media 2013