Dozens of vehicles crashed in a major car pileup on a bridge in the central city of Zhengzhou in Henan province because of extremely foggy conditions on Wednesday morning, broadcaster CCTV reported.

Several cars and trucks could be seen crumpled and piled on top of each other on the Zhengxin Huanghe bridge in pictures and videos on social media. One car was dramatically jack-knifed in the middle of a pileup in a snapshot from CCTV footage.

Many people were injured and trapped at the scene of the accident and the fire department was on the bridge.

Preliminary estimates from rescuers at the scene are that the pileup involved more than 200 vehicles and the injured were sent to hospital for treatment, according to local television reports.

A video on Weibo showed rows of cars and trucks in various states of damage with people meandering on the bridge taking videos and pictures.

One driver who seems to be the person filming said: "This is too scary. Full of people here. I don't think we can get off the bridge."

Visibility in multiple areas, including Zhengzhou, was less than 500 metres, and 200 metres in some areas this morning, according to the local meteorological service.

The Zhengxin Huanghe Bridge is a major overpass across the Yellow River, connecting Zhengzhou and neighbouring Xinxiang. (Reuters)