This photo taken on March 21, 2022 shows residents riding scooters and bicycles along a street after Shenzhen was reopened following a lockdown against a COVID-19 coronavirus outbreak in the Chinese metropolis. (STR / AFP)

SHENZHEN – The main districts of Chinese tech hub Shenzhen shut down public transport and extended curbs on public activities on Friday, as some cities in the Chinese mainland battled COVID-19 outbreaks.

Six districts comprising the majority of the city's population of almost 18 million announced that all residents would be tested twice for COVID-19 over the weekend as subway and bus services were suspended.

READ MORE: Shenzhen shuts electronics market to fight COVID outbreak

Employees should work from home, with the exception of those in self-contained "closed-loop" operations, essential supplies and public services.

According to the National Health Commission, the mainland on Thursday recorded 318 locally-transmitted confirmed COVID-19 cases, of which 128 were in Sichuan, and identified 1,567 local asymptomatic carriers in 24 provincial-level regions.

In the southwestern metropolis of Chengdu, which put its 21 million people under lockdown on Thursday, factories including plants run by auto giants Toyota and Volkswagen kept production running under closed-loops.

'Can’t just give up’

In Shenzhen on Thursday, city officials sought to quell rumours that a full lockdown was imminent. In March, the city swiftly locked down for a week to fight community infections.

We need to get the virus under control, we can't just give up like some countries.

Tang, Volunteer, Futian

They said people could leave and return to their homes with proof of a test result less than 24 hours old.

"We need to get the virus under control, we can't just give up like some countries," said a woman surnamed Tang volunteering to help food deliveries at a locked-down housing compound in Futian, Shenzhen's hardest-hit district.

On Friday, officials reported 87 new locally transmitted COVID infections in Shenzhen for Thursday, up from 62 a day earlier. Eight of the new cases were outside quarantine areas.

Closed loops

In Chengdu, daily mass testing will end on Sunday. The city reported 150 new local cases for Thursday, compared with 157 a day earlier.

Non-essential employees in Chengdu were told to work from home, while manufacturers capable of managing on closed campuses were exempted from work-from-home requirements.

Toyota Motor's Chengdu plant, which has an annual production capacity of 105,000 vehicles, was "operating normally" and inside a closed loop at the request of the Sichuan province government, a company official told Reuters.

ALSO READ: Shenzhen vows to mobilize all resources to curb COVID spread

A Volkswagen plant in Chengdu that makes the Sagitar and Jetta models has been operating in a closed loop since Thursday, a VW China representative told Reuters. Foxconn was continuing to operate a plant that makes Apple iPads in the city, Bloomberg reported.

However, Sweden's Volvo Cars, majority owned by China's Zhejiang Geely Holding Group, has shut its Chengdu plant, a company spokesperson said on Thursday.