Hundreds of workers can be seen marching on a road and confronted by riot police as well as people wearing hazmat suits In videos shared with AFP or circulated on social media.

Footage shared with AFP and captured by a factory worker showed one person lying inert on the ground next to a man in a blood-spattered jacket having his head bound in an apparent effort to staunch a wound.

Another clip shows dozens of hazmat-clad personnel wielding batons and chasing employees, one of whom is knocked to the ground before appearing to be kicked in the head.

Tech giant Foxconn on Wednesday confirmed the unrest.

The worker who shared the videos estimated that around 20 people were injured in the clashes, some of whom were taken to hospital. He requested anonymity to protect his safety.

The confrontations broke out after employees who signed an agreement with the factory to work at least 30 days in return for a one-time payment of 3,000 yuan ($420) suddenly saw the figure slashed to just 30 yuan, he told AFP.

Foxconn said workers had complained about pay and conditions at the plant but denied it had housed new recruits with Covid-positive staff at the Zhengzhou factory, the world's largest producer of iPhones.

Footage emerged this month of panicking workers fleeing the site on foot in the wake of allegations of poor conditions at the facility.

Multiple employees later recounted to AFP scenes of chaos and disorganization at the complex of workshops and dormitories.

"Regarding any violence, the company will continue to communicate with employees and the government to prevent similar incidents from happening again," the firm said in a statement.

Apple did not respond to requests for comment.

Foxconn, also known by its official name Hon Hai Precision Industry, is the world's biggest contract electronics manufacturer, assembling gadgets for many international brands.

Foxconn is China's biggest private sector employer, with more than a million people working across the country in about 30 factories and research institutes.

China is the last major economy wedded to a strategy of extinguishing Covid outbreaks as they emerge, imposing lockdowns, mass testing and lengthy quarantines despite the widespread disruption to businesses and international supply chains.

The policy has sparked sporadic protests throughout China, with residents taking to the streets in several major Chinese cities to vent their anger.