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.

Beijing's Capital International Airport reported morning visibility averaging between 250 to 500 meters.

Airport authorities said 13 flights had been canceled and 29 incoming flights were diverted to airports in neighboring cities and another five flights were forced to return.

Meanwhile, authorities in Tianjin said they had closed all 14 expressways in the northern municipality amid heavy smog.

In Hebei, 13 expressways were temporarily closed.

The Golden Week holiday, from Oct 1-7, is peak travel season with hundreds of millions of people on the move but plans were disrupted by long lines of slowly moving traffic made worse by the closure of expressways.

Wang Jichen, a Tianjin resident, said a trip from a local holiday resort in Jixian county back to downtown Tianjin took twice as long as normal as the highway was closed and drivers had to contend with poor visibility.

"After learning it would be foggy today, we dropped our sightseeing plans and returned ahead of schedule, hoping to avoid traffic jams. We set off at 6 am, but it didn't make any difference. We had to make a detour as the highway was closed and it took me more than four hours to get back home," he said.

The National Meteorological Center said the haze hanging over northern China, including the capital, neighboring Hebei and the port city of Tianjin would persist until Monday afternoon.

The Beijing Municipal Environmental Monitoring Center said on its website on Sunday that pollution levels in the city's six main districts were at 225-245. According to a table carried in the Beijing News, these readings correspond to Level 5 on the pollution scale. Anything above 300 is Level 6, China's highest.

A photo on the front page of the Beijing News showed the Forbidden City - a major tourist site - enveloped in thick haze on Saturday.

Xinhua -AP - AFP

(China Daily USA 10/07/2013 page2)