Heavy fog shrouded Urumqi, capital of northwest China's Xinjiang Uygur Autonomous Region, Saturday, and stranded thousands of passengers at the city's airport.

Heavy fog shrouded Urumqi, capital of northwest China's Xinjiang Uygur Autonomous Region.

The sixth incident of fog in the past seven days disrupted more than 100 flights Saturday morning, causing delays and cancellations, airport authorities said.

The Xinjiang branch of China Southern Airlines confirmed all 23 of its flights due to depart prior to 1 p.m. had been grounded and it was unclear when any would take off.

Zhang Xuejun, a passenger stranded at the airport, said visibility was no more than 50 meters and he saw no sign the fog would fade anytime soon.

Urumqi's weather bureau confirmed the city has had more foggy days than normal this month, but did not give exact details.