The sun sets above residential buildings on a hazy day in Beijing. [Photo/Agencies]

BEIJING, Dec. 15 (Xinhua) -- Beijing has issued its first red alert for air pollution this year, as a new bout of heavy smog is forecast to hit the city Friday, local environmental protection authorities said Thursday.

Approved by the municipal government, the red alert will be activated 8 p.m. Friday and is expected to be lifted on December 21 when the air quality in the city improves.

China National Environmental Monitoring Center said during the period, Beijing and neighboring Tianjin Municipality and Hebei Province will suffer a heavy air pollution, which will also affect Shandong and Henan provinces.

High polluting vehicles will be pulled off roads while other vehicles will be restricted based on an odd-or-even license plate rule.

Construction sites will be shut down, certain factories closed and schools advised to suspend classes during the red alert.

According to an updated emergency response plan for severe air pollution released November, four consecutive days of heavy air pollution, including two days of severe air pollution, activate a red alert.

A red alert is also issued if the city's Air Quality Index (AQI) reaches 500.