Thick smog has engulfed several cities in northeastern China bringing traffic to a standstill and closing at least one airport.
The top of the 75-storey skyscraper in Shenyang, Liaoning province was completely obscured by the choking fog
Air quality sensors in Harbin, the capital of Heilongjiang province, read 1,000 for particulate matter above a size deemed safe for human health.
A level above 300 is considered hazardous, while the World Health Organisation recommends a daily level of no more than 20.
The smog forced many primary and middle schools to suspend classes, and closed some public bus routes, the official Xinhua news agency reported.
The smog is expected to continue for the next 24 hours.