Smog covered much of China on Christmas Eve, including Beijing, where air pollution in some areas reached the index limit level.

Residents walk along a road during heavy smog in Beijing on Dec. 24.

For the whole of Tuesday, the city's PM 2.5 reading continued to rise, according to Beijing Municipal Environmental Monitoring Center. In the morning, the air quality downtown and in the south part of Beijing reached the hazardous level, and the pollution crept north through the afternoon.

Besides Beijing, seven other cities and provinces all over China are smogbound, according to the National Meteorological Center.

The air quality index (AQI) for 16 cities exceeded 300 on Tuesday, reaching the most severely polluted level. Of the ten most smoggy cities on Tuesday, seven were in north China's Hebei Province.

The AQI reading for the cities of Hebei, Shijiazhuang, Xingtai, Baoding and Handan reached, the top of the AQI monitoring meter.

Smog on Wednesday will continue until nightfall, when a cold front will bring rain and strong winds.

(Xinhua contributed to the story)