BEIJING - Smog began to cover parts of northern and central China from Sunday, and will cause medium-level or heavy air pollution in coming days, according to the National Meteorological Center (NMC).

Medium to heavy smog will hit parts of Beijing-Tianjin-Hebei next Tuesday and Wednesday, though it won't be as severe as the air pollution earlier this week, the NMC forecast.

All elementary and middle schools in Beijing will have to suspend outdoor activities as the city issued another orange alert for smog next week.

Elementary and middle schools, kindergartens and extracurricular training schools should suspend their activities outdoors during the alert from Monday to Wednesday, said the city's Commission of Education on Sunday.

The recent smog which dissipated on Tuesday prompted the Beijing municipal government to issue its first orange alert, the second-highest level, which means construction sites must stop dust-raising activities while the elderly and the children are advised to stay indoors.