Beijing on Friday issued its second air pollution 'red alert,' the highest emergency response level, in this winter, as a new round of heavy smog is forecast to choke northern China.

The 'red alert' will last 89 hours, taking effect from 7 am on Saturday until 12:00 am on Wednesday.

During the period, vehicles are only allowed on the roads based on odd or even license plate numbers. Kindergartens and primary as well as middle schools are advised to suspend classes and students can study at home.