Zhang Yao recalls the moment he realized something had gone deeply wrong at the Chinese mega-factory where he and hundreds of thousands of other workers assembled iPhones and other high-end electronics.

In early October, supervisors suddenly warned him that 3,000 colleagues had been taken into quarantine after someone tested positive for COVID-19 at the factory.

"They told us not to take our masks off," Zhang, speaking under a pseudonym for fear of retaliation, told AFP by telephone.

What followed was a weeks-long ordeal including food shortages and the ever-present fear of infection, before he finally escaped on Tuesday.

Zhang's employer, Taiwanese tech giant Foxconn, has said it faces a "protracted battle" against infections and imposed a "closed loop" bubble around its sprawling campus in central China's Zhengzhou city.

Local authorities locked down the area surrounding the major Apple supplier's factory on Wednesday, but not before reports emerged of employees fleeing on foot and a lack of adequate medical care at the plant.

Multiple workers have recounted scenes of chaos and increasing disorganization at Foxconn's complex of workshops and dormitories, which form a city-within-a-city near Zhengzhou's airport.

Zhang told AFP that "positive tests and double lines (on antigen tests) had become a common sight" in his workshop before he left.

"Of course we were scared, it was so close to us."

"People with fevers are not guaranteed to receive medicine," another Foxconn worker, a 30-year-old man who also asked to remain anonymous, told AFP.

"We are drowning," he said.

Those who decided to stop working were not offered meals at their dormitories, Zhang said, adding that some were able to survive on personal stockpiles of instant noodles.

Kai, a worker at in the complex who gave an interview to state-owned Sanlian Lifeweek, told the magazine Foxconn's "closed loop" involved cordoning off paths between dormitory compounds and the factory, and complained he was left to his own devices after being thrown in quarantine.

TikTok videos geolocated by AFP showed mounds of uncollected rubbish outside buildings in late October, while employees in N95 masks squeezed onto packed shuttle buses taking them from dormitories to their work stations.

A 27-year-old woman working at Foxconn, who asked not to be named, told AFP a roommate who tested positive for Covid was sent back to her dormitory on Thursday morning, crying, after she decided to hand in her notice while in quarantine.

"Now the three of us are living in the same room: one a confirmed case and two of us testing positive on the rapid test, still waiting for our nucleic acid test results," the worker told AFP.

Many became so desperate by the end of last month that they attempted to walk back to their hometowns to get around Covid transport curbs.

As videos of people dragging their suitcases down motorways and struggling up hills spread on Chinese social media, the authorities rushed in to do damage control.

The Zhengzhou city government on Sunday said it had arranged for special buses to take employees back to their hometowns.

Surrounding Henan province has officially reported a spike of more than 600 Covid cases since the start of this week.

When Zhang finally attempted to leave the Foxconn campus on Tuesday, he found the company had set up obstacle after obstacle.

"There were people with loudspeakers advertising the latest Foxconn policy, saying that each day there would be a 400 yuan ($55) bonus," Zhang told AFP.

A crowd of employees gathered at a pick-up point in front of empty buses but were not let on.

People in hazmat suits, known colloquially as "big whites" in China, claimed they had been sent by the city government.

"They tried to persuade people to stay in Zhengzhou... and avoid going home," Zhang said.

"But when we asked to see their work ID, they had nothing to show us, so we suspected they were actually from Foxconn."

Foxconn pointed to the local government's lockdown orders from Wednesday when asked by AFP if it attempted to stop employees from leaving, without giving any further response.

The company had on Sunday said it was "providing employees with complimentary three meals a day" and cooperating with the government to provide transport home.

Eventually, the crowd of unhappy workers who had gathered decided to take matters into their own hands and walked over seven kilometers on foot to the nearest highway entry ramp.

There, more people claiming to be government officials pleaded with the employees to wait for the bus.

The crowd had no choice as the road was blocked, AFP reported.

Buses eventually arrived at five in the afternoon -- nearly nine hours after Zhang had begun his attempt to secure transport.

"They were trying to grind us down," he said.

Back in his hometown, Zhang is now waiting out the home quarantine period required by the local government.

"All I feel is, I've finally left Zhengzhou," he told AFP.