BEIJING • Elementary and middle schools in Beijing will suspend outdoor activities this week after China's capital issued an orange alert for smog, according to the official Xinhua News Agency.

The suspension, which also covers kindergartens and extracurricular training schools, will remain in force from today to Wednesday, Xinhua said, citing the city's Commission of Education.

China, the world's biggest carbon emitter, plans to upgrade coal power plants in the next five years to reduce the pollutants and heavy smog that blanketed northern parts of the country last week.

Beijing on Nov 29 raised its air pollution alert for the first time in over a year to orange, the second- highest level in a four-tier system.

Beijing's skies have only just cleared after concentrations of PM2.5 - the pollutants that pose the greatest risk to human health - reached 666 micrograms per cubic metre on Dec 1. The World Health Organisation recommends average exposure over a 24-hour period of no higher than 25 micrograms per cubic metre.

With a lack of wind hampering the dispersion of pollutants, readings of PM2.5 near Tiananmen Square, in the centre of Beijing, had risen again to 117 by noon yesterday, the Beijing Municipal Monitoring Centre said on its website.

The National Meteorological Centre said smog had begun to cover parts of northern and central China from yesterday and will cause medium or heavy air pollution in coming days. It added that medium to heavy smog will hit parts of Beijing, Tianjin and Hebei tomorrow and Wednesday, although it was not expected to be as severe as last week's air pollution.

Emissions in northern China soar over winter as urban heating systems are switched on and low wind speeds means that polluted air does not get dispersed.

China is the world's biggest emitter of the greenhouse gases and is a crucial player in this month's global climate gathering in Paris, where nations are trying to thrash out a plan to limit global warming.

REUTERS, BLOOMBERG, AGENCE FRANCE-PRESSE