According to the Ho Chi Minh City Center for Disease Control and Prevention, by August 11, around 3,000 returnees who left central city Da Nang between July 1 and 28 have not declared their health status or getting tested.

Many had either refused to be tested or had registered for screening but did not show up.

If they fail to report themselves by the end of Friday, they can face criminal charges, HCMC Chairman Nguyen Thanh Phong said.

Around 140,000 people have returned to HCMC from Da Nang from July 1. After the country's first community transmission case in more than three months was confirmed in Da Nang on July 25, authorities nationwide have required Da Nang returnees to report themselves.

Vietnam’s protocols on Covid-19 prevention state all those that had visited stricken areas must be isolated and tested.

Another 625 people, including over 50 foreigners, are set to return to HCMC on Thursday and Friday after being stuck in Da Nang since July 28, when it suspended all public transport, including flights to and from the city.

All had tested negative, but once back in HCMC, will enter 14-day quarantine.

By Thursday, HCMC had recorded eight locally transmitted cases related to the Da Nang outbreak.

Da Nang has reported 310 domestic infections to date. The disease has spread to 13 other cities and provinces, including Hanoi.

So far, 20 patients have died.