SEOUL (REUTERS) - South Korea said on Wednesday (Nov 3) it would ramp up Covid-19 testing at schools after a sharp rise in infections among children, weeks ahead of a plan to fully reopen schools nationwide.

The surge comes as new social distancing rules aimed at a phased return to normalcy came into effect on Monday as a part of the country's plan to gradually move towards living with Covid-19 on the back of high Covid-19 vaccination rates.

South Korea has fully vaccinated nearly 90 per cent of its adult population, but began inoculating children aged between 12 and 17 only in recent weeks, administering just 0.6 per cent of the age group with both doses so far.

"There is a growing concern as the frequency of new cluster outbreaks has been increasing, centred on educational facilities such as private tuition centres and schools," Interior and Safety Minister Jeon Hae-cheol said.

The government will expand the use of portable polymerase chain reaction tests for Covid-19 in schools in Seoul and the neighbouring regions, and mobilise more virus-prevention personnel in overcrowded schools, he said.

South Korea plans to fully reopen schools nationwide from Nov 22.

The country reported 2,667 new cases for Tuesday, an increase of more than 1,000 from the day earlier. Nearly one-fourth of the new cases were found in teenagers, officials said.

"The teenagers spend a lot of time in communal living, such as in schools and tuition centres, and they are also active in social activities," Mr Son Young-rae, a senior Health Ministry official, told a briefing.

"We believe that the risk of infection will inevitably rise and the confirmed cases will continue to surge stemming from these teenagers."

South Korea has not seen a noticeable increase in seriously ill cases among teens, with just one out of 378 severe Covid-19 cases being treated in hospital. The country has also reported a relatively low mortality rate of 0.78 per cent.

Vaccination for the 12 to 17 age group began in October, using Pfizer-BioNTech shots.