A time-lapse video has demonstrated the extent of Beijing’s air pollution problem by capturing the point at which a thick layer of dark smog engulfed the city, rendering it virtually unrecognisable within the space of 20 minutes.

Chas Pope, who created the video, wrote on YouTube: “I made this earlier today [2 January] – a bank of AQ1400+ smog arriving in Beijing within the space of 20 minutes.”

His 12-second time-lapse video, dubbed “Beijing Airpocalypse,” appears to have been recorded from the window of one of the city’s skyscrapers and shows a thick brown cloud of smog sweeping into the city and engulfing its buildings.

The Chinese capital is known for its smog problem and on Tuesday it was placed on the second-highest orange smog alert, causing hundreds of flights to be cancelled and highways to be closed.

According to state news agency Xinhua, the smog is expected to continue in the region until the weekend, when a cold front moves in on 8 January.

China's weather bureau also issued its first ever fog red alert on Tuesday, saying that visibility could fall below 50 metres across northern China, while maritime safety agencies said poor visibility had forced three major ports to suspend the loading of ships.

Pollution alerts are common in northern China, especially during bitterly cold winters when energy demand, much of it met by coal, soars.

City officials have stated the air quality in Beijing is improving overall however. The Beijing Municipal Environmental Protection Bureau told state media that the total number of “blue sky days” reached 198 in 2016, an increase of 12 days on the previous year.

The country has been undergoing a “war on pollution” for the past three years in an attempt to reverse the damage caused to its skies, soil and water after decades of untrammelled economic growth.