JINAN - Dense fog around the Jinan International Airport has affected over 100 flights, airport authorities said Wednesday.

The fog had forced about 90 flights to be delayed and over 10 others to be canceled as of 11:30 am Wednesday, airport operators said.

The delays and cancellations have left more than 4,000 passengers stranded in Jinan, capital city of East China's Shandong province.

The fog is expected to disperse in the afternoon.

Heavy fog also swept the northern city of Tianjin, reducing visibility to less than 1,000 meters on Tuesday night. Visibility is expected fall below 500 meters on Wednesday night.

Tianjin meteorological authorities have issued a yellow alert, and some of the city's expressways have been closed. Yellow is the second lowest level in China's four-tier color-coded weather alert system.