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Pollution: Smog in Harbin
Thick smog enveloped a Chinese city for a third day Tuesday, forcing schools to close and bringing ground transport to a halt in places.
Highways were also shut and the regional airport shuttered after more than 250 flights were reportedly cancelled on Monday.
Visibility in some parts of the north-eastern city was reported to be as little as 10 metres (32 feet) and the density of airborne particles was reportedly several times above World Health Organisation recommended limit.
According to state media, the smog came as it activated its public heating system ahead of the frigid winter.
A top-level red alert for "thick smog or fog" was also issued for the entire province of Heilongjiang, which has Harbin as its capital, along with nearby Jilin and Liaoning.
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