A new spell of smog is expected to begin on Friday night and will continue until Sunday, when the north wind will clear the air, the National Meteorological Center said on Thursday.

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

The worst affected areas are likely to be the southern part of Beijing, the western part of Tianjin and the southern part of Hebei province. Residents in these regions may see heavy air pollution on Saturday and Sunday, according to a report on the center's website.

Smog forms when there is no wind or rain to drive away pollutants that accumulate close to the ground.

"The smog will not cover large areas, and there will not be the severe pollution seen last week," said Zhang.

Large parts of northern China experienced serious air pollution from Oct 7 to 11, with many cities — including Beijing — issuing high-level alerts and taking measures to reduce emissions.

Cities in Hebei, including Langfang, restricted the use of vehicles.