Beijing was put on yellow smog alert on Sunday, imposing restrictions on building and cooking outdoors.
The Air Quality Index in Beijing stood at between 200 and 300 out of 500 on Saturday and Sunday, meaning “very unhealthy”.
Forecasters said the pollution would continue on Monday and be dispersed by a cold snap on Tuesday. Smog had also affected Tianjin, Hebei and Shaanxi, the National Meteorological Centre said.
China has a four-tier system for air pollution, with red being the most serious, followed by orange, yellow and blue. Under the yellow warning, barbecues, work at construction sites and the burning of straw by farmers are not allowed.
Children, the elderly and people with respiratory or cardiovascular diseases are advised to stay indoors and people are advised to take public transport.
Environmental Protection Minister Chen Jining held an emergency meeting on Sunday to address the issue. Experts at the meeting said pollutants were concentrated because of weather conditions, Caixin reported.