BEIJING (Bloomberg) - Elementary and middle schools in Beijing will suspend outdoor activities from Monday to Wednesday after China's capital issued an orange alert for smog this week, Xinhua news agency reported on Sunday (Dec 6).

The suspension also covers kindergartens and extracurricular training schools and will remain in force during the alert, Xinhua reported, citing the city's Commission of Education.

Smog began to cover parts of northern and central China from Sunday, and will cause medium-level or heavy air pollution in coming days, according to the National Meteorological Center (NMC).

Medium to heavy smog will hit parts of Beijing-Tianjin-Hebei on Tuesday and Wednesday, though it won't be as severe as the air pollution earlier this week, the NMC said according to Xinhua.

China, the world's biggest carbon emitter, plans to upgrade coal power plants in the next five years to crack down on the kinds of 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 more than 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 meter on Dec 1. The World Health Organization recommends average exposure over a 24- hour period of no higher than 25 micrograms per cubic meter.

With a lack of wind hampering the dispersion of pollutants, readings of PM2.5 near Tiananmen Square in the center of Beijing rose again to 117 as of noon Sunday, the Beijing Municipal Monitoring Center said on its website.