China's environmental authority reported that 50 cities, including Beijing and Tianjin, were subject to heavy smog on Wednesday.

Among the 70 cities in the Beijing-Tianjin-Hebei region and environs, 30 cities are affected by "severe" air pollution, and 20 others are "heavily" polluted, the Ministry of Environmental Protection said.

The severe pollution in Beijing lessened after 3 p.m., the ministry said.

As of 3 p.m. Wednesday, 10 cities had issued red alerts against the smog.

The ministry named and shamed three organizations for environmental protection violations, pledging intensified supervision for air pollution prevention and control and heavier punishment for violations.