These high-risk areas should be governed by the government's Directive 16 that bans public gatherings of more than two people and asks people to stay home, stepping out only for emergencies, Long said.

The proposal was made at a meeting Monday after HCMC recorded five recent community transmissions, all being baggage handlers at Tan Son Nhat Airport and 25 of their close contacts who have tested positive for the virus and are awaiting Health Ministry confirmation as Covid-19 patients. The source of the new cluster at the airport has not been determined.

Prime Minister Nguyen Xuan Phuc agreed with the proposal at the meeting, saying that there have been seven areas in HCMC recording community transmissions, and social distancing should be applied in those areas.

The areas are in Districts 1, 9, 12, Binh Thanh, Go Vap, Binh Tan and Tan Binh.

HCMC applied social distancing under Directive 16 from April 1 to 22 last year.

Long said the outbreak in the baggage handling area at Tan Son Nhat could have existed long before and that some people involved may have been infected and then recovered.

"The outbreak in HCMC was quite complicated and has gone through many cycles of infection; therefore, the source of this outbreak has not yet been determined. This is what makes us very worried," he said.

The heath minister said even though they did not have contact with air passengers, the infected airport staff could still have interacted with many people in the community. He asked the city government to urgently prevent the outbreak from spreading further.

Deputy PM Vu Duc Dam said the "lucky things" are HCMC has been administering the face mask rule strictly, and that the patients are not infected with the new, fast-spreading mutant strains of the virus.

HCMC vice chairman Duong Anh Duc said the city will make efforts to restrict gatherings given the upcoming Lunar New Year holiday.

"Events and festivals that have been planned will be downsized as much as possible. Religious events and unneccesary activities will be suspended," Duc said.

As of Monday morning, several residential areas in HCMC have been locked down. Health staff are racing against time to track down all those in close contact with the confirmed patients and suspected cases for centralized quarantine and coronavirus testing.

HCMC has now recorded six locally transmitted cases, counting from Jan. 28 when community transmissions returned to Vietnam after 55 clean days, with the first case related to the cluster in northern Hai Duong Province.

In the past 11 days, Vietnam has registered 422 domestic cases in 12 cities and provinces.

Vietnamese will celebrate Tet, the country's biggest festival, this Friday but authorities in HCMC decided to cancel firework shows on Lunar New Year’s Eve amid the complicated development of the pandemic.