Heavy fog shrouded Chengdu, capital of southwest China's Sichuan Province, Friday morning, forcing authorities to close all major highways and the city's airport.

Boats are seen in heavy fog in Dalian, northeast China's Liaoning Province, Oct. 18, 2010. Some places in north China witnessed heavy fog on Thursday. [Xinhua]

The airport's administrators are still calculating the number of delayed flights.

Fog or haze also affected northern China cities, including Beijing and Shenyang, capital of Liaoning Province in the country's northeast.

Two highways linking Beijing with the northeastern city of Harbin and the northern municipality of Tianjin were closed Friday morning.

Zhang Mingying, a meteorologist at the Beijing Meteorological Bureau, said Beijing has been hit by haze for two days, which has caused a deterioration in air quality. A cold front is expected to disperse the pollution on Saturday.