The new cases in Lang Son and Bac Giang were mostly detected in isolation and lockdown areas related to workers working at industrial zones, while those detected in Hanoi are associated with previous outbreaks which have been placed into quarantine.
With the latest discovery, the nation has so far confirmed 5,665 local infections, and 1,503 imported ones.
Notably, a total of 4,095 locally-transmitted cases were found in the latest coronavirus wave that hit the nation in late April.
One day earlier, Vietnam registered 250 cases of local transmission, with the majority recorded in Bac Ninh and Bac Giang, the current largest epicenters in the latest COVID-19 outbreak. HCM City also saw the growing number of new local infections in recent times, with the majority are linked to the Revival Ekklesia Mission outbreak that was detected last week.
Amid the new outbreak in the southern metropolis, the municipal administration has decided to apply a range of social distancing measures, starting from zero hours May 31 in a bid to slow the spread of the pandemic to the wider community.
In addition, HCM City is planning a mass testing scheme on large scale, with a particular focus on sampling all members of the Revival Ekklesia Mission, which is the biggest COVID-19 hotspot in the city, and people who participated in the National Assembly and People's Council votes last week.
Over the past four days, the city has documented a total of 150 domestic infections in two clusters with the source of infection yet to be identified. In particular, the chain linked to the religious mission is the largest ever with 143 cases, while that of a couple in Tan Phu District has so far confirmed seven cases.
Meanwhile, more than 3,790 workers working in Bac Giang's industrial parks were vaccinated against COVOID-19 on May 30, bringing the overall number of vaccinated people in locality to 5,566 after four days of inoculation.