South Korea has reached another daily record in Covid-19 deaths as health officials reported more than 621,000 new infections on Thursday.

The figures underscore a massive Omicron surge that has been worse than feared and threatens an already over-stretched hospital system.

The 429 deaths reported in the latest 24 hours were nearly 140 more than the previous one-day record set on Tuesday.

Fatalities may rise further in coming weeks considering the intervals between infections, hospital admissions and deaths.

The total of 621,266 new coronavirus cases diagnosed by health workers was also a record daily jump, shattering Wednesday’s previous high of 400,624.

That pushed the national caseload to more than 8.2 million, with more than 7.4 million cases added since the start of February.

The outbreak has been significantly bigger than what had been forecast by government health authorities, who maintain that Omicron is nearing its peak.

Officials have tried to calm public fears amid concerns about a faltering pandemic response, saying that Omicron is no more deadly than seasonal influenza for vaccinated people and less dangerous than the Delta strain that hit the country hard in December and early January.

South Korea still has a much lower rate of Covid-19 deaths in relation to size of population than the United States or many European nations, which officials attribute to high vaccinations with more than 68% of the population having received booster shots.

However, some experts say health officials clearly underestimated how the greater scale of the outbreak would strain worn-out hospital workers following the recent Delta surge. They criticise the government for sending the wrong message to the public by easing social distancing restrictions and effectively communicating that Omicron is mild.

Transmissions were probably worsened by an intense presidential campaign leading up to last week’s election, which also appeared to have reduced political capacity to maintain a stringent virus response.

Lee Sang-won, a senior Korea Disease Control and Prevention Agency official, said during a briefing that health authorities feel “apologetic” over the explosion of Omicron cases that has been bigger than they expected.

He said around 70,000 of the new cases reported on Thursday were infections that were mistakenly omitted from Wednesday’s tally, and that the real daily increase would be around 550,000.

Omicron has forced South Korea to abandon a stringent Covid-19 response based on mass laboratory tests, aggressive contact tracing and quarantines to focus limited medical resources on priority groups, including people 60 and older and those with pre-existing medical conditions.

Health officials have recently significantly eased quarantine restrictions and border controls and stopped requiring adults to show proof of vaccination or negative tests when entering potentially crowded spaces such as restaurants so that more public and health workers could respond to rapidly expanding at-home treatments.

Nearly two million virus carriers with mild or moderate symptoms have been asked to isolate at home to save hospital space.