Ten new deaths on Wednesday carried the toll to 349, after 3277 infections the previous day, while the ICU utilisation rate is nearing 80 per cent, despite a population that is 84 per cent fully vaccinated, with 14 per cent receiving booster doses.

"The infection numbers are unusually high today, mostly due to many COVID-positive cases detected by the testing laboratories within a few hours in the afternoon," the health ministry said in a statement.

"The Ministry of Health is looking into this unusual surge in cases within a relatively short window, and closely monitoring the trends for the next few days," it added in Wednesday's statement.

While nearly 98.7 per cent of the past month's 90,203 cases had no symptoms, or only mild ones, about 0.2 per cent of those had died, and 0.1 per cent each were being monitored closely in intensive care units (ICU) or were critically ill and intubated there.

About 72 ICU beds were vacant by Wednesday, at an overall ICU use rate of 79.8 per cent, with 142 coronavirus sufferers accounting for about half of occupied beds.

The ministry said it was adding more ICU beds. The Asian city-state, which has set aside 200 ICU beds to be used by COVID-19 patients, can add 100 more at short notice.

Last week, it extended some social curbs for about a month, to rein in the spread of COVID-19 and ease pressure on healthcare facilities.

Authorities reinstated curbs limiting social interactions and dining out to two people, so as to slow infections.

Australian Associated Press