Beijing city government has issued a red alert for severely high levels of air pollution in the city for three days from December 17 to 21, according to a post on the Beijing environmental protection bureau's official Weibo account.

The incoming smog was due to an accumulation of air pollution in Beijing and surrounding areas, including Tianjin city and Hebei, Shandong and Hunan provinces, the post said, citing forecasts from the China Environmental Monitoring Center.

A colour-graded warning system of alerts was introduced in China's capital city last year as part of the government vow to crackdown on environmental degradation following decades of unbridled economic growth.

People told to stay indoors as air pollution in Beijing reaches hazardous levels Show all 5 1 /5 People told to stay indoors as air pollution in Beijing reaches hazardous levels People told to stay indoors as air pollution in Beijing reaches hazardous levels beijing-1.jpg A woman wearing a mask crosses a road during severe pollution in Beijing GETTY People told to stay indoors as air pollution in Beijing reaches hazardous levels beijing-2.jpg A woman wearing a mask walks on a street during severe pollution in Beijing GETTY People told to stay indoors as air pollution in Beijing reaches hazardous levels beijing-3.jpg Parking attendants stand on a roadside during severe pollution in Beijing GETTY People told to stay indoors as air pollution in Beijing reaches hazardous levels beijing-4.jpg Traffic makes its way through Beijing GETTY People told to stay indoors as air pollution in Beijing reaches hazardous levels beijing-5.jpg Severe pollution clouds the Beijing skyline GETTY

Beijing's first ever red alert was issued in December last year, temporarily closing schools and halting construction in the city.

The government has since been tweaking the system, raising in February the threshold of issuance to a higher average daily air quality index reading.