A man flies a knight in Pudong district in Shanghai, shrouded by smog on Dec 6, 2013. [Photo/icpress.cn]

Shanghai halted some factories and kept a third of its public transport vehicles from roads on Dec 6 to cope with one of the city's worst smog levels this year.

The city's air quality index reached 437 at noon, which indicates hazardous pollution.

The government issued an official notice on Friday afternoon to stop production of certain industrial enterprises as well as closures of outdoor construction projects. Thirty percent of public transport vehicles were not allowed on roads.