China's national observatory on Tuesday renewed a yellow alert for thick fog in some parts of the country.

Heavy fog was forecast to affect parts of the provinces of Jiangsu, Zhejiang, Fujian and Guangdong, Guangxi Zhuang Autonomous Region, and Chongqing Municipality on Tuesday morning, according to the National Meteorological Center.

Visibility in some affected areas was expected to be reduced to less than 200 meters, the Center said.

Motorists are advised to control their speed to ensure safety in heavy fog, while precautionary measures should be taken at airports, expressways and ferry terminals for safe travel.

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