BEIJING, Nov. 30 (Xinhua) -- Beijing has issued a yellow alert Friday for heavy air pollution as a round of smog will hit the city at the weekend, local authorities have said.

Smog in Beijing (Photo: VCG)

A series of measures will be taken from Saturday, including the suspension of a number of outdoor construction operations, the restriction of heavy-polluting vehicles, and the production halt or restriction of some manufacturing companies, according to the municipal air pollution emergency response office.

The yellow alert is issued when the air quality index surpasses 200 for two consecutive days.

Due to adverse weather conditions, the Beijing-Tianjin-Hebei region will be affected by the smog. The air quality is expected to improve on Sunday evening.

Under Beijing's current three-tier color warning system, yellow alert is the least severe, followed by orange and red.