Vietnam has suspended all flights to and from Danang for 15 days after at least 22 cases of the novel coronavirus had been detected in or around the city, the government said on Tuesday.
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, and seven in Danang and nearby Quang Nam province on Tuesday.
All bus and train services to and from Danang have also been suspended from Tuesday, a government statement said.
The city, a tourism hot spot, reintroduced social distancing measures over the weekend after confirmation of a resurgence of domestically-transmitted cases.
With more than 95 million people, Vietnam is the most populous country in the world yet to report a Covid-19 fatality. Thanks to strict quarantining and aggressive and widespread testing, Vietnam has kept its infection tally to 438 cases.
Two of the Danang cases were in a critical condition, the health ministry said.
Vietnam is still closed to foreign tourism, but there had been a surge in domestic travellers capitalising on 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 increase flights from Danang to 11 Vietnamese cities to help evacuate 80,000 people, mostly tourists.
"All evacuation flights now are cancelled," CAAV deputy director Vo Huy Cuong told Reuters.
"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."
About 18 000 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, the capital's governing body on Monday.