A police officer directs traffic amid the fog in Chaoyang district yesterday. [Mirror Evening News]

Transport ground to a halt as heavy fog enveloped parts of China Wednesday forcing airports and expressways to close to traffic.

In the southwest China's Sichuan Province, the cities affected included Chengdu, the provincial capital, Dazhou, Leshan and Meishan, according to local meteorologists.

In Chengdu, Shuangliu International Airport closed at around 6:50 a.m., as visibility fell below 50 meters. It resumed normal operations at around 11 a.m. when the fog dispersed.

During the closure, 105 flights to and from Shuangliu were delayed and more than 10,000 passengers were stranded. Some of the incoming flights were forced to land at airports in nearby Chongqing and Kunming cities.

At least four expressways, including the routes between Chengdu and Dujiangyan and between Dazhou and Chongqing, were closed in the morning.

Beijing, the nation's capital, was also blanketed in fog early Wednesday.

Prior to 9 a.m., visibility at the Capital International Airport in Beijing was around 50 meters, rising to 500 meters after 10 a.m.. Many flights were delayed, said a north China aviation control department spokesman, but without revealing the exact number.

Tianjin sections of Beijing-Tianjin-Tanggu and Beijing-Shanghai expressways were closed in the morning because of the fog.

Meteorologists in Beijing believed the fog spread to Beijing from the adjacent Hebei Province.

Heavy fog blankets Urumqi, northwest China's Xinjiang Uygur Autonomous Region, November 25, 2009. [Xinhua]

In northwest China's Xinjiang Uygur Autonomous Region, more than 4,000 passengers were stranded at the airport of Urumqi, the regional capital, Wednesday as some 132 domestic and international flights were canceled or delayed due to the heavy fog, according to the airport management.

Visibility in the airport dropped to about 300 meters at noon and the fog is estimated to linger in the city in the coming 12 hours, according to the latest weather forecast.

When the flights will resume remained unknown.

In east China's Shandong Province, heavy fog had delayed some 40 flights and closed a number of highways Wednesday. About 30 of the delayed flights have taken off and almost all the affected highways had reopened to traffic by 5 p.m..

The station said fog will continue to blanket part of the province until Thursday morning, reducing the visibility to less than 200 meters in some localities.

According to the forecast from the National Meteorological Center at 6 p.m., heavy fog is expected to reduce visibility to below 1,000 meters in Beijing and Tianjin municipalities and areas in 13 provinces including Shanxi, Shandong and Sichuan.