Few words could better describe the weather in Beijing yesterday than the Chinese idiom "flying sand and rolling pebbles" as the capital city was gripped by its second smog-choked dust storm in less than 10 days.
Strong, dry winds struck the city at about 10am, bringing a wall of dust from the Mongolian frontier, reducing the already poor visibility from lingering haze on Thursday and Friday, and disrupting flights and high-speed trains.
While Beijing residents hunkered down indoors, some of the 5,000-plus delegates attending the annual legislative and political advisory sessions in the capital braved the chilly winds and choking sands.
For the first time, police on Beijing streets were seen wearing black masks designed to filter health-threatening PM2.5 pollutants and bacteria.
The roof of Beijing Capital International Airport's Terminal 3 was partly ripped open by a sudden whirlwind - at speeds of up 30 metres per second - at midday, the airport said.
Photos circulating on microblogs showed pieces of yellow roofing insulation that were blown onto the aircraft parking apron.
No casualties were reported.
At least 41 flights were cancelled and another 125 delayed, while the gales forced high-speed trains from Beijing to Tianjin , Shanghai and Guangzhou to reduce speed.
The overall air quality index in Beijing soared to 500 at 11am and did not start to drop until 3pm.
At noon, levels of larger PM10 pollutants surpassed 1,000 micrograms per cubic metre - 20 times the World Health Organisation's recommended safety - at a downtown monitoring station, prompting health concerns.
"Seriously, which is more harmful, the lingering smog caused by industrial pollution or the sandstorms from Mongolia?" asked a microblogger on Sina Weibo.
Similar, if not worse, conditions affected cities across the north of the country.
Air quality indices in Lanzhou, Gansu province, Hohhot, Inner Mongolia autonomous region and Xining, Qinghai province, topped 1562, 1445 and 1339 respectively at 1pm.
In Tianjin, winds brought down billboards and brick walls, crushing cars parked nearby. A parked Air China passenger jet was blown into a boarding bridge at the airport, but there were no casualties, Sina's news portal reported.