Meteorological authorities on Saturday issued an alert for heavy fog across the country's eastern regions as a cold front will bring rains and snow to the central and northern regions.

Heavy fog hung over Beijing for the fourth consecutive day Saturday. [Chinanews.com]

Heavy fog will hit eastern China and the cities of Beijing and Tianjin in the north, said the National Meteorological Center (NMC). Large parts of southern China will also be affected by foggy weather.

Visibility will drop to less than 1 km, or even below 500 meters, according to the NMC's forecast.

At least five interprovincial expressways in Beijing were closed early Saturday for safety considerations, including the expressways linking to Harbin in the northeastern province of Heilongjiang, Shanghai, Hong Kong, Tianjin and Hebei.

Daily air quality reports released by the China Environmental Monitoring Center indicated Beijing's air was polluted for four consecutive days since Wednesday.

The NMC reminded residents living in those regions to take precautions and reduce their outdoor activities due to the low air quality brought by the fog.

The NMC said that a cold front will drop temperatures by between four and eight degrees Celsius in the north as strong winds will also sweep the region over the next three days.

Some areas in Inner Mongolia and the northeast will experience snow while rains will hit the southern part of Shaanxi Province and the central regions, according to the forecast.