A new spell of smog is expected to begin on Friday night and affect areas like Beijing, which experienced heavy pollution last week.

The smog will continue until Sunday night, when the north wind will disperse the pollutants, the National Meteorological Center said on Thursday.

It will affect central and northern parts of the country, including Beijing and Tianjin, as well as Hebei, Shanxi, Henan and Shandong provinces, said Zhang Fanghua, the center's chief forecaster.

"The pollution in Beijing may rise to a serious level at some time, while the visibility will be around three to seven kilometers at most times," Zhang said.

But the smog will not cover large areas, and will not be as severe as the pollution seen last week, according to a report on the center's website.

Confronted with frequent heavy pollution, the Ministry of Environmental Protection will implement monthly inspections on provincial and municipal efforts to control the pollutant emissions from this October to March next year, the ministry said on Wednesday.

Officials and monitors will go directly to the sites without informing the local environmental authorities. In some cases, they will conduct undercover investigations. Polluters will be punished, the ministry said.

In addition, the ministry has sent drones to inspect key areas of Tianjin, Hebei, Shanxi and Shandong, where air pollution in cities is often the highest in China.

Smog gathers when there is no wind or rain to drive away pollutants that accumulate close to the ground. During the previous heavy hazy days from Oct 7 to 11, the calm weather failed to disperse the pollutants, choking residents in dozens of cities.

In addition, burning fields of straw was considered a major source of the smog, the Ministry of Environmental Protection said. In Henan, the environmental watchdog monitored 7,893 burning sites during the National Day holiday.

Many cities, including Beijing, issued a high-level alert and put strict reins on emissions. Langfang in Hebei province, for example, restricted the use of private cars during last week's smoggy spell.

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