HANOI - Vietnam widened lockdown measures in its industrialised north on Tuesday to combat its biggest COVID-19 outbreak so far, as authorities reported a daily record in new cases that was more than double the previous high.

The health ministry late on Tuesday announced 447 new COVID-19 infections, the biggest jump since the 190 cases seen on May 16, driven by clusters in factory zones in Bac Ninh and Bac Giang provinces. The figure was revised from 457 announced earlier.

"The COVID-19 variant found this time has been spreading very rapidly and widely," Health Minister Nguyen Thanh Long said in a statement, without specifying which variant.

Vietnam has reported the presence of the highly contagious variant first identified in India.

The outbreak has spread to more than 30 of Vietnam's 63 cities and provinces, including the capital Hanoi, which has shut restaurants and banned public gatherings.

Bac Ninh, home to production facilities of Samsung Electronics, started a curfew and other travel restrictions from Tuesday, state media reported.

That followed the temporary closure of four industrial parks, including three with Foxconn facilities, by authorities in neighbouring Bac Giang province.

The outbreak could be a big challenge for Vietnam, which successfully contained earlier, smaller outbreaks and avoided the level of economic damage suffered by its neighbours.

Hundreds of factory workers are among the nearly 2,800 people infected since late April, which accounts for about half of the country's 5,773 overall cases. It has recorded 44 deaths.

"The density of workers at the outbreak is so high, sharing the same enclosed environment, the same dining areas and the same sanitary areas," Long said.

"The risk is very high."

Most cases on Tuesday were at factories in Bac Giang, where authorities said testing was ramped up and workers' dormitories closed off.

The local government said it was considering a partial resumption of operations from Wednesday for workers not infected.

Vietnam has yet to start mass inoculations against the coronavirus, with about 1 million vaccine doses administered so far. REUTERS