Beijing issues three-day major smog alert

Heavy industry in Beijing will have to limit output by 30-to-50 per cent from Monday to Wednesday after a major smog alert was declared.

Beijing's environmental protection bureau has declared a smog alert for three days. Source: AAP

Beijing declared its third major smog alert of this year, and the second this month, just a day after being named the top performer among 28 Chinese cities that took special measures to rein in pollution.

Saturday's orange alert, the second-highest in a four-level system after red, will run from Monday to Wednesday, the Beijing environmental protection bureau said in a post on its official Weibo microblog account.

The central part of the Beijing-Tianjin-Hebei region is forecast to see medium to heavy pollution over the three days, it added.

An orange alert requires factories that make furniture, cement and other heavy industry to limit output by 30-to-50 per cent.

More than 700 companies figure among the affected firms in the capital.

Beijing achieved the biggest reduction in average pollution among 28 northern cities from October to February, the bulk of a winter heating season that ended on March 15, the newly formed Ministry of Ecology and Environment said last week on Weibo.