Beijing, Dec 26: Thousands of passengers across eastern, northern and central China have been stranded after heavy fog closed airports and hundreds of flights were cancelled, state media said today.

Highways were also closed and in some cities, such as Lanzhou in the northwest, authorities issued pollution alerts and warned people not to go outside as smog had worsened the situation, Xinhua said.

''In some provinces, people are advised to wear masks as the heavy smog contains pollutants like carbon monoxide,'' Xinhua said.

Airports in Nanjing, Hangzhou and Hefei in China's east and Jinan in the north either closed completely or cancelled most flights, it said, stranding around 20,000 people.

''No flights have taken off since this morning,'' an official at Nanjing airport said by telephone, adding he not know when the situation would return to normal.

The fog is expected to dissipate as freezing air from Siberia moves across China, Xinhua said, though temperatures would fall by up to 10 degrees Celcius.

Two people died in road accidents caused by the poor weather, the official Xinhua news agency said.

REUTERS