The smog that has shrouded the northern parts of the country since last week will persist until Thursday, China's environmental watchdog said.

In Beijing, the measurement of PM2.5 - particulate matter with a diameter less than 2.5 micrograms, which can go deep into the lungs and is extremely harmful to people's health - soared to the hazardous level of 276 on Monday, the Ministry of Environmental Protection said.

Tianjin and many cities in Hebei and Shandong provinces were also hit by heavy air pollution, with Xingtai and Dongying having PM2.5 readings above 250.