A woman with a child turns around her scooter after a landslide blocked a road following heavy rains brought by Typhoon Molave in central Vietnam’s Quang Nam province on Thursday. Molave has killed 16 people and caused dozens missing in the country. Photo: AFP

 Vietnam confirmed its first outbreak of the coronavirus in 55 days on Thursday and warned it could be more serious than its last wave of infections, as authorities rushed to contain the spread and test tens of thousands of people.

The health ministry earlier on Thursday reported two locally transmitted cases, the country's first in 55 days, one of which was exposed to an individual who had tested positive in Japan for the more contagious B117 variant first discovered in the UK.

The 83 infections announced on Thursday, were a new daily record for Vietnam which has effectively closed its borders and avoided the larger epidemics seen by its neighbors. Previously the country had recorded just over 1,550 cases and 35 deaths since the virus was first detected.

The outbreak, in Hai Duong and Quang Ninh provinces near the capital Hanoi, is the biggest in Vietnam since a cluster emerged in the central city of Danang in July and quickly spread to most regions of the country, leading to its first coronavirus fatalities.

"We think the outbreak in Hai Duong will be worse than the one in Danang," Health Minister Nguyen Thanh Long said at an urgent meeting on the sidelines of the Communist Party's five-yearly Congress.

"We will take tens of thousands of samples for testing today," he told the meeting.

Long said Vietnam had so far not seen so many tests come back positive: a total of 72 out of 138 people to have come into contact with one of the two new cases reported on Thursday morning testing positive for the virus, Long said.

The outbreak will be a jolt for Vietnam, which, owing to strict quarantine, testing and tracing measures, has kept the virus in check, earning it a top-two spot in a survey of how well countries have handled the pandemic.

A village and an electronics factory was locked down on Thursday, with 2,340 workers quarantined in Hai Duong and huge contact tracing efforts launched.

Containment efforts could be complicated by an upcoming Lunar New Year holiday period, when big gatherings indoors are typical.