A man wearing a mask takes a selfie in front of Tian'anmen Square in Beijing on Dec 8, 2015. [Photo/IC]

Under the red alert, vehicles are only allowed on the roads based on odd or even license plate numbers, and the government will cut its use of vehicles by 30 percent.

On Monday, the Beijing Municipal Environmental Bureau said governments in Beijing, Tianjin and Hebei had inspected 1,112 enterprises and work sites, and found problems at 45 of them.

Public education institutions from kindergartens to high schools will be closed during the red alert.

Inspections will continue during the three-day red alert and a daily news release will be issued, officials said.

Chai Fahe, deputy director of the research academy under the Ministry of Environmental Protection, said if Beijing faces up to the current situation realistically, it will encourage other cities to follow suit and not hide their problems.

In Heibei province, the cities engulfed by the latest smog wave include Shijiazhuang, Langfang, Baoding, Xingtai, Hengshui, Handan, Dingzhou and Xinji.

Residents of Langfang are being allowed to use public transportation for free when smog affects the city.

In Handan, authorities said their focus will be on restricting coal-burning and industrial discharges, which is expected to result in a 15 percent cut in emissions.

Throughout the Beijing-Tianjin-Hebei area, major monitoring targets include power plants, steel and metal works, and coking and cement factories, environmental officials said.

The Ministry of Environmental Protection warned that parts of Shanxi and Shandong provinces will be heavily affected.

Beijing experienced its first serious smog this winter from Nov 29 to Dec 2, when an orange alert was issued, even when readings of some hazardous airborne particles rose to 940 at one time. A reading of 75 is rated as normal in China. Widespread public complaints were leveled at the government for not raising the alert level to red.

Wang Yanfei contributed to this story.