China's national observatory on Wednesday issued a yellow alert for heavy fog in some parts of the country.

From Wednesday evening to Thursday morning, thick fog is expected to overshadow parts of Hebei, Beijing, Tianjin, Henan, Anhui, Jiangsu, Hubei, the Sichuan Basin and Chongqing, according to the National Meteorological Center (NMC).

In some regions of Hebei, Henan, the Sichuan Basin and Chongqing, visibility may be reduced to below 200 meters, the NMC said.

Drivers have been asked to maintain safe speeds, and airports, freeways and ports have been instructed to take appropriate safety measures.

China has a three-tier, color-coded warning system for thick fog, with red being the most serious warning, followed by orange and yellow.