Dense fog affected Shandong, Hubei, Hunan, Jiangxi and Fujian provinces with visibility below 200 m (656 ft) while some parts of southern Jiangsu and southern Anhui had visibility below 50 m, China's National Meteorological Centre said.
The Central Meteorological Observatory issued yellow and orange warnings for heavy fog up to 7:45 a.m. (2345 GMT). Haze is expected in many areas going into Friday, Chinese weather forecasters predicted.
Some areas of Anhui issued red warnings for heavy fog - the most serious advisory - and many highways were temporarily closed, according to state media broadcaster CCTV news.
In Nanjing, capital of China's eastern Jiangsu province, several areas were hit by extreme fog causing snarls in public transportation to varying degrees, CCTV reported.
China has a three-tier colour-coded warning system for thick fog, with red being the most serious, followed by orange and yellow.
The fog also caused dozens of scheduled flights out of Shanghai Pudong International Airport to be delayed or diverted over the last three hours, according to FlightView.com's flight tracking app.
A Reuters witness flying to Harbin from Shanghai reported that her plane was delayed for hours.
"We just returned to the gate, so it looks like forever," said the frustrated traveller, revealing a photo of a wall of dense grey mist outside a plane window that was covered with rain drops.
(Reporting by Bernard Orr; Additional reporting by Nicoco Chan in Shanghai and Shanghai newsroom; Editing by Jacqueline Wong)
By Bernard Orr
