Passengers wait in the Terminal 3 at the Beijing Capital International Airport, Dec 4, 2011. [Photo/Xinhua]

BEIJING - Dense fog shrouded Beijing on Sunday evening and disrupted more than 100 flights and closed off expressways.

A source with the Beijing Capital International Airport said the airport was forced to cancel 82 departing flights and delayed another 54 for at least one hour as of 9:30 pm Sunday.

Poor visibility from the fog also forced several expressways surrounding Beijing to be temporarily closed, and traffic authorities have warned of extended gridlock in the city.

The Beijing Meteorological Center on Sunday afternoon issued a code yellow alert to warn about heavy fog in the capital, saying visibility would drop to less than 500 meters in most parts of the city.