China has again warned residents in large parts of the north of the country to prepare for choking smog over the weekend, the worst of which is expected over Beijing, prompting the capital to issue its second ever "red alert".

China's Meteorological Administration said on Friday that the smog would stretch from Xian, across part of central China, through Beijing and up into Shenyang and in the country's freezing northeast.

"Beijing, central-western Tianjin, central-southern Hebei, western Shandong and southern Shanxi will get heavy air pollution," the administration said in a statement.

Beijing issues highest alert over air pollution

"The worst weather condition will be seen in some parts of southern Beijing and central-southern Hebei."

The warning came as the Chinese capital enjoyed clear blue skies on Friday.

The air pollution is expected to begin rolling in from Saturday evening and will last until Tuesday. Visibility in the worst affected areas, such as Beijing, is likely to fall to less than 1km, and possibly even less than 200m in some areas.

The pollution index will probably exceed 500 in Beijing and parts of Hebei province, which surrounds the capital, the agency said. Residents are encouraged to remain indoors at levels higher than 300, according to government guidelines.

During the warning period, vehicle restrictions are put in place based on licence plate numbers and 30 percent of government-owned cars are taken off the road. Public education institutions are advised to suspend classes.

The Beijing city government issued its first "red alert" last week following criticism that previous bouts of smog had failed to trigger the highest warning level.

Beijing's second red alert comes after a landmark climate agreement was reached in Paris earlier this month, setting a course to move away from a fossil fuel-driven economy within decades in a bid to arrest global warming.

Source: Al Jazeera And Reuters