Readings for PM2.5, hazardous particles measuring 2.5 microns in diameter or less, exceeded 200 micrograms per cubic meter at 9 a.m. in some areas, said the Beijing Environmental Protection Monitoring Center.

　　Moderate or serious air pollution was reported in many parts of Beijing, with a visibility of no more than 500 meters in the early morning, the center added.

　　The visibility at Beijing Capital International Airport at one point fell to 5 to 10 meters, delaying some flights.

　　Beijing stretches of expressways linking to other cities including Kaifeng, Harbin, Shanghai and Tianjin were temporarily closed, Beijing municipal traffic administration authorities said.

　　The provinces of Tianjin, Hebei and Henan were also affected by heavy smog on Sunday.

　　The air quality index reached 500, or extreme pollution, in five monitoring sites at 8 a.m. in Shijiazhuang, the provincial capital of Hebei.

　　Prolonged smog hit many Chinese cities in January.