Speaking at an online meeting with the government on Wednesday, he said: "People in the city have started to neglect regulations on Covid-19 prevention. For that, I propose that the government should work on a strategy of gradually tightening restrictions and firming up regulations so that we can finally achieve victory."

He did not specify on what tougher measures should be taken.

He said the city has the epidemic under control with no new cases in the last eight days and only five in the last 15, 88 percent less than in the previous 15 days.

This was thanks to the social distancing campaign between April 1 and 15, the early response by the city as well as its drastic moves to isolated infected areas and public awareness of the need to follow the rules, he said.

But the disease remains unpredictable, he said, citing cases in which one patient had an incubation time of more than 14 days and another tested negative and was discharged only to be found positive again.

The latter, patient 22, a British man discharged from hospital in the central city of Da Nang on March 27, tested positive again in HCMC where he came to leave for the U.K. He had come into contact with dozens of people in the city before leaving the country.

"If we loosen the rules, we could lose the battle," Phong warned.

So far city officials have fined over 5,000 people VND100,000-300,000 ($4.26-12.78) for not wearing a face masks in public.