Beijing is under an extreme smog warning Sunday, with pollution at hazardous levels for a third day, and people warned to stay indoors.
The municipal environment warning center issued an alert Saturday in China's capital, advising the elderly, children and those suffering respiratory or cardiovascular illness to avoid going out or doing strenuous exercise.
The center said Sunday that particulates small enough to deeply penetrate lungs were at nearly four times the level considered safe. The readings were called the worst on record.
China's official state-run Xinhua news agency predicted that the pollution could last another three days.
Meanwhile, fog covering vast areas of eastern and central China has closed numerous highways and delayed flights in several provinces.
International organizations say China's air quality is among the worst in the world because of massive coal consumption and car-choked city streets.
Some information for this report was provided by AP, AFP and Reuters.