An eerie 12 second long time-lapse video of smog choking the city of Beijing gives a glimpse of the serious air pollution problem in the Chinese capital.

The video shows the smog descending over the city and engulfing buildings during a 20-minute period.

The hazardous air quality conditions started last Friday (30 December) and are expected to persist until the weekend.

Chas Pope, a British engineering consultant working in Beijing, captured the footage.