Beijing has upgraded its alert for air pollution from orange to red, the most serious level today, state-run Xinhua news agency reported.
This is the first time the capital has issued the red alert, which will last from 7:00 AM Tuesday to 12:00 PM Thursday.
The notice, issued after days of heavy smog last week, also places traffic restrictions on certain types of vehicles in the city of 22.5 million people.
Yesterday China's weather observatory issued a yellow alert for smog that will cover the country's northern regions and asked schools to keep the children not let them outdoors to avoid exposure to heavy smog.
Beijing, Tianjin, parts of the neighbouring provinces of Hebei, Henan and Shandong, as well as parts of eastern Jiangsu province will be shrouded in moderate smog and the southern part of Beijing will be choked by heavy smog, the National Meteorological Center (NMC) said.