Government authorities have launched traffic control measures and suspended factory production in order to curb the pollution.

In the city of Jinan in east China's Shandong province, the local government on Tuesday cut the number of both government and private vehicles on the road in half according to their license plate numbers, allowing even-numbered license plate owners to drive on some days and odd-number drivers to drive on others. The measure is in effect until further notice.

Experts have urged local governments to exert concerted efforts to reduce the smog.

Ma Jun, director of Beijing's public environment research center, said factories in neighboring cities have affected the city's air quality.

Factories can be seen in large numbers in the cities of Tangshan, Shijiazhuang and Handan, all of which are located south of Beijing in Hebei province.

"On Saturday morning, the sky was still blue in some parts of Beijing, but it became smoggy by noon because of wind bringing polluted air from the south," Ma said.

Ma advised municipalities, provinces and autonomous regions in north China, including Beijing, Tianjin, Hebei, Shanxi, Henan, Shandong, Inner Mongolia and Liaoning, to work together to come up with a joint method to reduce pollution.