Beijing suffered its worst air pollution of the year on Monday, with monitoring sites throughout the city reporting extremely hazardous levels of pollutants.
City authorities issued a rare orange alert, the second highest of four danger levels.
. Pedestrians wear masks as they make their way through Beijing on Nov. 30.
Visibility was cut to several hundred yards, as buildings receded into thick smog.
. A woman wears a mask on a polluted day in Beijing on Nov. 30.
. People pass by Tiananmen Square during heavy pollution on Nov. 30.
. Motorists ride on a street shrouded in smog in Beijing on Nov. 30. Beijing issued an orange alert for heavy smog, the highest level this year. Authorities in the Chinese capital warned of 'severe pollution' and advised the capital's 20 million inhabitants to stay indoors.
. A couple wears protective masks as they walk outside the Forbidden City on Nov. 30 in Beijing.
. Buses and cars cause heavy traffic on roads in Beijing on Nov. 30.
. A baby is held inside a vehicle stranded on a highway between Beijing and Hebei province, China, that is closed due to smog on Nov. 30.
. People walk past the giant portrait of late Chinese Chairman Mao Zedong, at the Tiananmen Gate in Beijing on Nov. 30.
. Pedestrians and police cross the street at a crosswalk at Tiananmen Square in Beijing on Nov. 30.
. An official wears a mask due to the pollution in Beijing on Nov. 30.
. A couple wearing face masks talk at bus station on Nov. 30 in Beijing, China.