Targeted testing and strict quarantining had helped Vietnam contain earlier outbreaks, but it is battling a new cluster of infections after going more than three months without detecting any domestic transmission.

The new outbreak has infected more than 200 people since July 25, the majority in the central city of Danang, but it has spread to at least eight other cities and provinces, including Hanoi and Ho Chi Minh City, where entertainment venues are closed and gatherings restricted to prevent infections.

Danang and Buon Ma Thuot in the coffee-growing Central Highlands have been placed on lockdown. A government spokesman on Monday said Vietnam does not plan a nationwide lockdown.

More than 88,000 people have returned to Hanoi from Danang since July 8, but only 70,689 were tested, the health ministry said. Only two of those were positive.

The gap is due to a shortage of rapid testing kits used to screen thousands of residents at a time, according to state media.

The health ministry said it would assign Hanoi medical institutions and hospitals to boost testing capacity.

The rapid test kits, which can diagnose a blood sample in minutes but are prone to inaccuracies, are used to identify potentially positive cases which are then confirmed with the more accurate, swab-based Polymerase Chain Reaction (PCR) test.

Phan Quoc Viet, chairman of test kit manufacturer Viet A Corp, said he was not concerned about stocks.

"Vietnam is not short," Viet told Reuters. "We have enough for two million PCR tests and are willing to provide enough kits for the country to conduct a widespread testing program".