Concerned about the damage done to its reputation by persistent smog, the municipal government promised in January that it would take "extraordinary" measures this year to curb emissions from coal consumption and cars.

China is also considering tough new measures restricting industrial activity in the region surrounding Beijing, according to a draft policy document seen by Reuters.

Gasoline-powered vehicles that fail to meet China's Emission Standard III will not be allowed to enter the city's main districts on weekdays, and drivers will be fined if they fail to comply, Xinhua said late on Monday.

Beijing was one of 24 cities to issue a smog "red alert" at the end of last year, allowing authorities to impose emergency restrictions on traffic and industrial output in order to reduce emissions.

The 5.7 million vehicles on Beijing's roads account for 31 percent of the city's hazardous breathable particles known as PM2.5, a major constituent of smog. Cars are also estimated to be responsible for more than 80 percent of the carbon monoxide in China's air.

China has drawn up new rules requiring all light vehicles to adhere by 2020 to its strictest "China VI" emission standards, which are based on ones used in Europe and the United States.

New cars in Beijing will have to adhere to the China VI standards from this year.