SEOUL (REUTERS) - South Korea reported on Wednesday (Dec 1) a new daily record of 5,123 coronavirus cases, as the country battles to contain a sharp rise in patients with severe symptoms and stave off the Omicron variant.

The surge began in early November after the country started relaxing Covid-19 rules, and the government said on Monday it would hold off a further easing because of the strain on its healthcare system and the possible threat posed by the new variant.

Experts warned that cases would continue to rise until unvaccinated people obtained immunity through infections, as the country has fully inoculated nearly 92 per cent of its adults and now focuses on vaccinating children and a booster programme.

Although neighbouring Japan has contained transmission, and kept new cases in Tokyo to a single-digit numbers, South Korea is following a trend seen in many other countries, experts said.

Singapore, which has among the world's highest vaccination rates and maintains strict Covid-19 rules, had a surge in infections and deaths for more than two months until it started stabilising recently.

"To slow the pace of the current wave of infections, the authorities could bring down the number of cases by re-introducing some of the social distancing measures," Dr Jung Jae-hun, a professor of preventive medicine at Gachon University.

South Korea said hospitals were treating 723 patients with severe Covid-19, a record number.

That is a steep rise in severe cases compared with just under 400 in early November.

Now nearly 90 per cent of ICU beds in the greater Seoul area are occupied, with 842 patients waiting for beds.

To ease the strain on hospitals and care centres, South Korea this week began making at-home treatment the default for people with mild infections, with only more severe cases transferred to hospitals.

Residential treatment centres will also be expanded.

The Korean Medical Association (KMA) urged the government to set up treatment facilities and allow antibody treatment for high-risk patients before they develop severe symptoms.

It also urged the government to suspend quarantine exemptions temporarily for some entries to prevent the Omicron variant.

South Korea has not reported any confirmed Omicron cases so far but is investigating suspected cases in travellers coming from Nigeria.

Authorities will mobilise the administrative structure to secure hospital beds, at least an additional 1,300 by mid-December, Interior and Safety Minister Jeon Hae-cheol told a Covid-19 response meeting.

More than 84 per cent of the severely ill Covid-19 patients were aged 60 and above.

Experts had pointed to waning antibody levels from the vaccines and urged the elderly to get booster shots.

Tuesday's new cases bring the coronavirus infections in the country to 452,350 cases, with 3,658 deaths.

Despite the rising hospitalisation rate, the mortality rate remains relatively low at 0.81 per cent, according to the government data.

South Korea has fully vaccinated nearly 80 per cent of its 52 million people, and will expand its booster programme to adults ages 18 to 49 on Saturday.