The Southeast Asian country is back on high alert after authorities on Saturday confirmed the first community infections since April, and another three cases on Sunday, all in or around Danang.

A further 11 cases linked to a Danang hospital were reported late on Monday.

All bus and train services to and from Danang have also been suspended from Tuesday, the statement said. The city, a tourism hot spot, had reintroduced social distancing measures over the weekend after the government confirmed the first domestically-transmitted cases of coronavirus in more than three months.

With more than 95 million people, Vietnam is the most populous country in the world to have recorded no COVID-19 fatalities. Thanks to strict quarantine measures and an aggressive and widespread testing program, Vietnam has kept its virus total to 431 cases.

Two of the Danang cases were in a critical condition, Vietnam's health ministry said.

Vietnam is still closed to foreign tourism, but there had been a surge in domestic travellers looking to take advantage of discounted flights and holiday packages to local resorts.

On Monday, the government said it had requested the Civil Aviation Authority of Vietnam (CAAV) to allow domestic airlines to significantly increase the number of flights from Danang to 11 Vietnamese cities in order to help evacuate 80,000 people, mostly tourists.

"All evacuation flights now are cancelled," CAAV deputy director Vo Huy Cuong told Reuters by phone on Tuesday.

"We operated 90 flights to evacuate tourists stranded in Danang yesterday but most tourists had already left Danang on Sunday, mostly by coach or train to nearby provinces," Cuong said.

Around 18,000 of the tourists who had been in Danang have returned to Ho Chi Minh City, authorities from the southern business hub said on Tuesday.

A further 15,000 to 20,000 had been expected to arrive in Hanoi, according to a statement from the city's governing body on Monday.