Smog has lowered visibility to less than 50 meters in parts of northeast China, leading to the weekend closure of highways and an airport.
The transport authority in Liaoning province says seven expressways were partly or wholly shut on Sunday.
More roads and an airport shut farther north in Heilongjiang province, which borders Russia.
Xinhua News Agency said the airport in Harbin city cancelled all 209 inbound and outbound flights on Saturday. The airport said flights are operating again Sunday as visibility improved to a few hundred meters.
Last month, Harbin practically ground to a halt with a particularly bad bout of pollution.
China's national meteorological center says the haze would gradually be reduced owing to a cold front and rain.