The city, which had already halted indoor restaurant service and closed salons as well as gyms, also stopped rail and bus passenger services to and from provinces in the south which have seen the biggest increases. Hanoi has seen only over 400 cases since May, compared with more than 50,000 across the country, but authorities had already imposed restrictions on several parts of the city after the discovery of new outbreaks.

Vietnam has managed to keep coronavirus cases relatively low due to targeted mass testing and strict contact tracing, border controls and quarantine measures, but new clusters of infections in recent weeks have triggered concern among health officials. "This outbreak is not the same as the previous ones," health minister Nguyen Thanh Long said at a meeting on COVID-19 prevention on Sunday. "We are preparing and standing ready for worse and worst scenarios."

Strict restrictions were earlier introduced in southern areas of the country where three-quarters of the recent infections were detected. The country's civil aviation authority on Sunday ordered domestic airlines to suspend flights to and from southern parts until at least Aug. 1.

Long said the health ministry had sent 2,000 ventilators and tens of thousands of its most highly-qualified health workers to the south. Hard-hit areas would also be prioritised for around seven million rapid COVID test kits due to arrive Vietnam next week. Vietnam's daily COVID-19 cases hit new record of 5,926 infections, raising its total cases to 53,830.

The Southeast Asia country also registered an extra 29 deaths from July 4-17, raising its total death toll due to COVID-19 to 254. Those deaths had initially not been reported due to technical errors, the health ministry said. (Editing by Kirsten Donovan and Philippa Fletcher)