Major urban areas face reduced visibility, increased accidents over the weekend, Wu Wencong reports in Tianjin and Beijing.

China's most developed regions were attacked by smog over the weekend.

A total of 104 cities in 20 provinces in and near China's two largest industrial clusters - the Beijing-Tianjin-Hebei region and the Yangtze River Delta region - fell victim to heavy smog that reduced visibility to less than 10 meters in some places, according to the Environmental Protection Ministry.