A swirling yellow sandstorm has slammed into Beijing, with residents warned to stay indoors and air traffic grinding to a standstill.
More than 50 flights were reportedly cancelled in the Chinese capital as a cloud of dust enveloped large parts of the centre and north of the country.
Beijing’s 10 million-strong population were advised to wear masks or scarves outdoors, while children and the elderly were told to stay indoors.
By 9pm local time, air concentrations of fine pollution particles, called PM2.5, had soared to above 600 micrograms per cubic metre, according to air quality website aqicn.org. The World Health Organisation's safe limit is 25.
Meanwhile measurements of larger PM10 particles, thought to contribute to lung cancer and other respiratory illnesses, were even higher, at over 900.
China has suffered heavy pollution in recent years, particularly in winter when many burn coal to heat their homes.
Smog is famous with Beijing residents, prompting frequent complaints on social media, but China is also affected by dust storms, which occur in springtime and have been exacerbated as deserts grow larger due to climate change.
This sandstorm, swiftly dubbed an "airpocalypse" on Twitter, began at the southern edge of the Gobi desert, according to data from green group the Institute of Public and Environmental Affairs.