BEIJING - China's environment ministry says pollutants were reduced by a third in Beijing during this week's temporary restrictions to reduce heavy smog, which included taking half the city's cars off the roads.

Beijing's authorities ordered limits on cars, factories and construction sites for three days during a red alert for smog starting Tuesday. They also told schools to close.

The Ministry of Environmental Protection said Wednesday that the emergency measures cut pollutant emissions by 30 per cent from 7 a.m. to 5 p.m. Tuesday.

Beijing imposed the red-alert - the highest on a four-colour scale - following a forecast of high pollution for three consecutive days.

On Thursday, the air quality had improved to a moderate level from previously hazardous levels, according to the U.S. Embassy's air quality index.