Smog descended over Beijing and North China at the weekend, shrouding the city and its famous cultural landmarks in a thick haze, and forcing authorities to close expressways and airports.

Heavy smog hit the capital for a second consecutive day on Sunday and visibility was less than 1 km in downtown areas.

As of 10 am on Sunday, traffic police had closed six inter-province expressways, including roads linking the capital with Harbin in the northeast, Shanghai in the east, as well as those leading to neighboring Tianjin and Hebei province.