Beijingers woke up Saturday to find the Chinese capital blanketed in yellow dust, as a sandstorm caused by a severe drought in the north and in Mongolia swept into the city.
The storm, which earlier buffeted parts of northeastern China, brought strong winds and cut visibility in the capital.
Authorities issued a rare level five pollution warning, signalling hazardous conditions, and urged residents to stay indoors.
Sandstorms frequently hit the arid north of China in the spring, when temperatures start to rise, stirring up clouds of dust that can travel across China, to South Korea and Japan and even as far as the United States.
Scientists blame a combination of deforestation and prolonged drought in northern China for the phenomenon.
Saturday's storm was expected to last until Monday, the meteorological agency said in a statement on its website.
"I was amazed to see the ground had turned yellow overnight," Beijing salesman Li Ming told the official Xinhua news agency. "It reminds me of the dirt road of my rural hometown."
Another resident said the storm was worse than those in recent years.
"Severe sandstorms like this happened very often in the 1980s and 1990s," Beijing retiree Song Xiurong told Xinhua. "It hasn't been that serious in the recent two or three years, as far as I remember."
Xinhua reported that the storm, which came after an unusually humid winter and numerous blizzards, caught residents of the capital by surprise.
"The snow has certainly curbed local dust from flowing but sandstorms cannot disappear altogether as long as their origins still exist," meteorological agency chief Guo Hu told the agency, adding that the vast deserts of China's Inner Mongolia region were just 800 kilometres (500 miles) from Beijing.
A sandstorm four years ago dumped at least 300,000 tonnes of sand on the capital.
China has 2.6 million square kilometres (one million square miles) of desert, an area nearly 2.5 times the country's total farmland, according to government statistics released at the time.
In the southwest of the country, drought has left 16 million people with a shortage of drinking water, according to a statement issued by the State Commission of Disaster Relief.
Since late last year, the provinces of Yunnan, Sichuan and Guizhou, have received only half their annual average rainfall, leaving water supplies severely depleted.
More than four million hectares (10 million acres) of land were affected and 4,000 troops have been deployed to help distribute emergency water supplies, Xinhua said.
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