Beijing, Oct 6 (IANS): Heavy fog that shrouded most parts of China Sunday has forced the authorities to close down several airports and expressways.

In Beijing, heavy smog lasted into the second day Sunday and visibility was under 1,000 metres in the downtown areas, reported Xinhua.

As of 10 a.m., traffic police authorities had closed down six interprovincial expressways, including roads linking the capital with Harbin in the northeast, Shanghai in the east, as well as Tianjin and Hebei province.

Beijing's Capital International Airport reported even lower visibility Sunday morning, averaging 250 to 500 metres.

Despite the foggy weather, airport authorities said 159 departing flights had taken off as of 9.30 a.m., accounting for 56 percent of the total planned takeoffs. Thirteen flights were cancelled.

Poor visibility at the airport caused 29 incoming flights to land at airports in neighbouring cities and forced another five to return.

Meanwhile, authorities in Tianjin said they had closed down all 14 expressways amid heavy fog.

In Hebei province, 13 expressways have been closed until visibility improves.

Foggy weather has also affected most parts of Liaoning province. As of Sunday morning, 15 expressways have been closed down.

In China's industrial city of Anshan, visibility was under 50 metres in some areas and many travellers were forced to postpone their trips.

Sunday is the sixth day of the week-long holiday for China's National Day and large number of travellers are heading home from their tours.