North China's Hebei province is on red alert in the face of three days of heavy smog. This is the first high-level warning issued by the province this year.

Northern Hebei Province on red alert for heavy smog

The province's Air Pollution Prevention and Control office says smog will cover eight cities from Friday to Sunday. Most cities in the province's central and southern parts have been placed under red alert.

In some cities, cars have been banned from the streets depending on the last digits of their plate numbers. In the city of Xingtai, factories have been told to cut emissions by half, while construction sites are ordered to suspend operations.

A red alert is the most serious level for air pollution in a four-tier warning system. It's issued when a city's Air Quality Index is projected to reach 500.