Hon Hai Precision (Foxconn), Huawei and ZTE were reportedly among some 100 companies impacted by fresh restrictions on production imposed by Chinese city Shenzhen, following a rise in Covid-19 (coronavirus) cases.
Yicai Global reported the companies were told to shift to closed-loop production for seven days, which requires staff to remain at facilities.
Companies affected included Semiconductor Manufacturing International Corp, the news outlet reported.
The Shenzhen Municipal Bureau of Industry and Information Technology sent notices to the companies on 24 July. The city reported 21 Covid-19 cases on 23 July and 19 a day earlier.
Yicai Global stated the move to closed-loop working conditions aims to avoid a full lockdown, and keep production and supply chains stable.
China continues to press on with a zero-Covid goal, locking-down cities and sending anyone testing positive or in close contact with a positive case to quarantine centres.