BEIJING -- Beijing on Saturday night issued an orange alert for air pollution in the coming days, advising children and the elderly to stay indoors.

The alert, the second highest level, will last from Monday to Wednesday, said Beijing's air pollution emergency response office.

Beijing, Tianjin, Hebei and their neighboring regions are forecast to see severe air pollution from Sunday to Wednesday, according to China National Environmental Monitoring Center.

In Beijing, the air will gradually improve from Wednesday night when a cold front arrives.

Some manufacturers will reduce production and some construction sites will halt work. Heavily polluting vehicles and trucks carrying construction waste and dirt are banned from roads, according to the city's air pollution emergency response plan.

According to the plan, an orange alert should be issued when the average air quality index is forecast to exceed 200 for three consecutive days and and one of those day is forecast to be over 300.

Under China's four-tier warning system, red is the most severe, followed by orange, yellow and blue.